Light source apparatus, projector, and light source apparatus drive method

ABSTRACT

A light source apparatus includes an arc tube having a first electrode and a second electrode that carry out an emission of light due to a discharge between them, and a drive that, when supplying energy in an alternating current to the first electrode and the second electrode, carries out a steady operation supplying a steady energy to the first electrode and the second electrode, and an initial operation making a cumulative energy supplied to at least one electrode, of the first electrode and the second electrode, in an anode period of the relevant electrode, prior to the steady period, greater than during the steady period.

This application claims priority from Japanese Patent Application No.2007-268700 filed in the Japanese Patent Office on Oct. 16, 2007, andJapanese Patent Application No. 2008-167386 filed in the Japanese PatentOffice on Jun. 26, 2008, the entire disclosures of which are herebyincorporated by reference in their entirety.

BACKGROUND

1. Technical Field

The present invention relates to a light source apparatus equipped witha discharge lamp having a pair of electrodes, and a drive methodthereof, as well as a projector in which such a light source apparatusis embedded.

2. Related Art

An electrode of an ultra-high pressure mercury lamp embedded in adischarge light emitting type light source apparatus erodes as a littime elapses, a length and a position of an arc changes, and an originof a discharge is not stable in one place, causing a flicker. In orderto remedy this, a technology of smoothing out a surface and newlyforming a projection thereon, by temporarily making a current magnitudelarger at a steady time and fusing an electrode leading extremity, hasbeen known (refer to Japanese Patent No. 3840054).

However, when changing a current value during a lighting operation witha steady power, as an illuminance of a light source changes along withit, a brightness of a projection image changes, and there is a danger ofhaving an adverse effect on a performance as a video instrument. Also,the electrode leading extremity being of a comparatively normal shape ata stage at which an aging has not progressed too far, carrying out thefusion of the electrode leading extremity at this time results in makingthe arc length unnecessarily long.

SUMMARY

An advantage of some aspects of the invention is to provide a lightsource apparatus, and a drive method thereof, which enable an improvingof a condition of an electrode while inhibiting an occurrence of anilluminance fluctuation during the lighting operation with the steadypower.

Another advantage of some aspects of the invention is to provide aprojector in which the heretofore described light source apparatus isembedded.

A light source device according to an aspect of the invention includes(a) an arc tube having a first electrode and a second electrode thatcarry out an emission of light due to a discharge between them, and (b)a drive that carries out a steady operation supplying a steady energy tothe first electrode and the second electrode and, before carrying outthe steady operation, carries out an initial operation supplying energyto the first electrode and the second electrode, with an operationdiffering from the steady operation. (b1) The drive, in the initialoperation, carries out a fusing drive making a volume of a fused portionof a leading extremity side of at least one electrode, of the firstelectrode and the second electrode, greater than a volume of the fusedportion of the leading extremity side of the at least one electrode at atime of a rated drive during the steady operation.

With the heretofore described light source apparatus, the drive cancarry out a fusing drive, in the initial operation, melting a leadingextremity side of at least one electrode, of the first electrode and thesecond electrode. With the fusing drive, at any timing during theinitial operation, as the volume of the fused portion of the leadingextremity side of at least one electrode is made greater than the volumeof the fused portion of the leading extremity side of the at least oneelectrode at the time of the rated drive during the steady operation, arepair or a restoration of the electrode utilizing a lighting startperiod is possible. That is, it being possible, with the fusing driveduring the initial operation, to melt and smooth out a surface of aprotruding leading extremity formed on a leading extremity side of oneelectrode, and of a leading extremity side area on a periphery thereof,it is possible to suppress an occurrence of a flicker and an arc jump.Also, with the fusing drive during the initial operation, it beingpossible to reproduce the protruding leading extremity along withmelting and smoothing out the protruding leading extremity formed on theleading extremity side of one electrode, and the periphery thereof, itis possible to suppress an occurrence of a flicker and an arc jump. As aresult, as well as being possible to maintain an illuminance of anillumination light from the light source apparatus, it is possible tolengthen a life span of the light source apparatus. According to theabove, as the fusion volume of the electrode is increased withoutinterrupting or changing the steady operation, it is possible to preventa brightness of a source light or projection image from fluctuating dueto the fusing drive during the steady operation.

Also, according to a specific aspect or standpoint of the invention, thefusing drive of the initial operation and the rated drive of the steadyoperation both supplying energy in an alternating current to the firstelectrode and the second electrode, by a cumulative energy supplied toat least one electrode, in an anode period of the relevant at least oneelectrode, at a time of the fusing drive of the initial operation beingmade greater than a cumulative energy supplied to the at least oneelectrode, in the anode period of the relevant at least one electrode,at a time of the rated drive during the steady period, the volume of thefused portion is increased. In this case, by relatively increasing thecumulative energy supplied in the anode period of at least one electrodeat the time of the fusing drive, compared with at the time of the rateddrive, it being possible to reliably increase a temperature of theleading extremity of the at least one electrode, it is possible toincrease the volume of the fused portion of the leading extremity sideto a desired extent. In the event that it were possible, by anadjustment of the cumulative energy supplied in the anode period of theat least one electrode, to increase a maximum temperature of the leadingextremity of the at least one electrode, it can be supposed that itwould be possible to increase the volume of the fused portion thereof.Furthermore, in the event that it were possible, by an adjustment of thecumulative energy, to increase an average temperature during the anodeperiod of the relevant at least one electrode, it can be supposed thatit would be possible to increase the volume of the fused portionthereof.

Also, according to a specific aspect or standpoint of the invention, aregular initial drive and the fusing drive of the initial operation, andthe rated drive of the steady operation, all supplying energy in analternating current to the first electrode and the second electrode, bya cumulative energy supplied to the leading extremity of at least oneelectrode, when the relevant at least one electrode is the anode, at thetime of the fusing drive of the initial operation being made greaterthan a cumulative energy supplied to the leading extremity of the atleast one electrode at the time of the rated drive during the steadyperiod, the volume of the fused portion is increased. In this case, byrelatively increasing the cumulative energy supplied to the leadingextremity of the at least one electrode, compared with at the time ofthe rated drive, it being possible to reliably increase the temperatureof the leading extremity of the at least one electrode, it is possibleto increase the volume of the fused portion of the leading extremityside to a desired extent. In the event that it were possible, by anadjustment of the cumulative energy supplied to the at least oneelectrode in a latter half of the anode period of the at least oneelectrode, to increase the maximum temperature of the leading extremityof the at least one electrode, it can be supposed that it would bepossible to increase the volume of the fused portion thereof.Furthermore, in the event that it were possible, by an adjustment of thecumulative energy supplied in the latter half of the anode period of theat least one electrode, to increase an average temperature during onecycle, it can be supposed that it would be possible to increase thevolume of the fused portion thereof.

Also, according to another aspect of the invention, the fusing drive ofthe initial operation and the rated drive of the steady operation bothsupplying energy in an alternating current to the first electrode andthe second electrode, by a maximum value of a current supplied in ananode period of at least one electrode, at the time of the fusing driveof the initial operation, being made greater than a maximum value of acurrent supplied in an anode period of the at least one electrode at thetime of the rated drive during the steady period, the volume of thefused portion is increased. In this case, by relatively increasing themaximum value of the current supplied in the anode period of at leastone electrode at the time of the fusing drive, compared with at the timeof the rated drive, it being possible to reliably increase thetemperature of the leading extremity of the at least one electrode, itis possible to increase the volume of the fused portion of the leadingextremity side to a desired extent. In the event that it were possible,by an adjustment of the maximum value of the current supplied in theanode period of the at least one electrode, to increase the maximumtemperature of the leading extremity of the at least one electrode, itcan be supposed that it would be possible to increase the volume of thefused portion thereof. Furthermore, in the event that it were possible,by an adjustment of the maximum value of the current supplied in theanode period of the at least one electrode, to increase the averagetemperature during the anode period of the relevant at least oneelectrode, or during one cycle, it can be supposed that it would bepossible to increase the volume of the fused portion thereof.

According to still another aspect of the invention, the drive, in alaunching operation period including at least a period immediatelybefore switching to the steady period, during the time of the fusingdrive of the initial operation, increases a value of a current suppliedto the at least one electrode as time elapses. In this case, thetemperature of the at least one electrode gradually increasing duringthe launching operation period, it is possible to increase the volume ofthe fused portion of the leading extremity side of the relevant at leastone electrode.

According to still another aspect of the invention, the light sourceapparatus further including an evaluating portion that determines adegree of erosion of the arc tube, the drive, in the fusing drive of theinitial operation, increases a rate of increase of the value of thecurrent supplied to the at least one electrode during the launchingoperation period, in accordance with the degree of erosion determined bythe evaluating portion. In this case, in the launching operation, it ispossible to deal with a tendency for concavities and convexities formedon the leading extremity side of the electrode to become difficult tomelt along with a temporal aging.

According to still another aspect of the invention, the drive, in thefusing drive of the initial operation, increases the value of thecurrent supplied to the at least one electrode at an end of thelaunching operation provided after a start of the initial operation. Inthis case, the temperature of the at least one electrode increasessharply at a final stage of the launching operation, and it is possibleto increase the volume, of the fused portion of the leading extremityside of the at least one electrode.

According to still another aspect of the invention, the drive, in thefusing drive of the initial operation, in the event that a voltagebetween the first electrode and the second electrode reaches apredetermined voltage value, temporarily increases the value of thecurrent supplied to the at least one electrode compared with that beforereaching the predetermined voltage value. By this means, it beingpossible to further increase the temperature in a condition in which theelectrode is sufficiently preheated, it is possible to reliably increasethe volume of the fused portion.

According to still another aspect of the invention, the light sourceapparatus further including an evaluating portion that determines thedegree of erosion of the arc tube, the drive, in the fusing drive of theinitial operation, increases the value of the current supplied to the atleast one electrode at the end of the launching operation period, inaccordance with the degree of erosion determined by the evaluatingportion. In this case, in the launching operation, it is possible todeal with the tendency for the concavities and convexities formed on theleading extremity side of the electrode to become difficult to meltalong with the temporal aging.

According to still another aspect of the invention, the drive, in thefusing drive of the initial operation, makes an anode duty ratiorelating to a current to one electrode, of the first electrode andsecond electrode, greater than at the time of the rated drive at thetime of the steady operation. In this case, it being possible torelatively increase the energy supplied to the relevant one electrode,it is possible to reliably increase the fusion volume.

According to still another aspect of the invention, the light sourceapparatus further including an evaluating portion that determines thedegree of erosion of the arc tube, the drive, in the fusing drive of theinitial operation, increases the anode duty ratio relating to therelevant one electrode in accordance with the degree of erosiondetermined by the evaluating portion. In this case, in the launchingoperation, it is possible to deal with the tendency for the concavitiesand convexities formed on the leading extremity side of the electrode tobecome difficult to melt along with the temporal aging.

According to still another aspect of the invention, the drive, in thefusing drive of the initial operation, superimposes a direct current, ofa polarity the same as an anode of the relevant one electrode, on thealternating current supplied to the first electrode and the secondelectrode. In this case, as a direct current of a polarity the same asthe anode of the relevant one electrode is superimposed on thealternating current, it being possible to relatively increase the energysupplied to the relevant one electrode, it is possible to reliablyincrease the fusion volume.

According to still another aspect of the invention, the light sourceapparatus further including an evaluating portion that determines acondition of the arc tube, the drive, in the fusing drive of the initialoperation, increases the direct current to be superimposed on thealternating current supplied to the first electrode and the secondelectrode in accordance with the degree of erosion determined by theevaluating portion. In this case, in the launching operation, it ispossible to deal with the tendency for the concavities and convexitiesformed on the leading extremity side of the electrode to becomedifficult to melt along with the temporal aging.

According to still another aspect of the invention, the drive, at thetime of the fusing drive of the initial operation, making a currentwaveform supplied to at least one electrode a superimposed wave, whereina triangular waveform is superimposed on a rectangular wave and acurrent gradually increases over a half cycle, a proportion of a maximumcurrent value of the current waveform, with respect to an averagecurrent value in the anode period of the at least one electrode, at thetime of the fusing drive is greater than a proportion of a maximumcurrent value with respect to an average current value in the anodeperiod of the at least one electrode in the rated drive of the steadyoperation. In this case, it being possible to relatively increase thetemperature of one electrode, it is possible to increase the fusionvolume.

According to still another aspect of the invention, the light sourceapparatus further including an evaluating portion that determines thecondition of the arc tube, the drive, at the time of the fusing drive ofthe initial operation, increases the proportion of the maximum currentvalue of the current waveform with respect to the average current valuein the anode period of at least one electrode, at the time of the fusingdrive, in accordance with a degree of erosion determined by theevaluating portion. In this case, in the launching operation, it ispossible to deal with the tendency for the concavities and convexitiesformed on the leading extremity side of the electrode to becomedifficult to melt along with the temporal aging.

According to still another aspect of the invention, the drive, as anaspect of the fusing drive of the initial operation, can carry out, forone fusing drive, either one of a first fusing drive, which melts theleading extremity side of the first electrode more than the leadingextremity side of the second electrode, or a second fusing drive, whichmelts the leading extremity side of the second electrode more than theleading extremity side of the first electrode. Also, the drive, bycarrying out the second fusing drive as a fusing drive of a currentinitial operation in the event that the first fusing drive has beencarried out as a fusing drive of an immediately preceding initialoperation, and carrying out the first fusing drive as the fusing driveof the current initial operation in the event that the second fusingdrive has been carried out as the fusing drive of the immediatelypreceding initial operation, alternately makes the first electrode andthe second electrode a main fusion subject. In this case, it beingpossible to fuse the leading extremity side of the first electrode andthe leading extremity side of the second electrode in a balanced manner,it is possible to avoid a smoothing out, a restoration or a reproductionbeing executed unevenly.

A drive method of the light source apparatus according to an aspect ofthe invention carries out the steady operation supplying the steadyenergy to the first electrode and the second electrode of the dischargelight emitting type arc tube and, before carrying out the steadyoperation, carries out the initial operation supplying energy to thefirst electrode and the second electrode, with an operation differingfrom the steady operation. The method includes carrying out the fusingdrive making the volume of the fused portion of the leading extremityside of at least one electrode, of the first electrode and the secondelectrode, in the initial operation greater than the volume of the fusedportion of the leading extremity side of the at least one electrode atthe time of the rated drive during the steady operation.

With the heretofore described drive method, as the volume of the fusionportion of the leading extremity side of at least one electrode, at anytime during the initial operation, is made greater than the volume ofthe fusion portion of the leading extremity side of the at least oneelectrode at the time of the rated drive during the steady operation, arepair or a restoration of the electrode utilizing the lighting startperiod becomes possible. Therefore, as well as being possible tomaintain the illuminance of the illumination light from the light sourceapparatus, it is possible to lengthen a life span of the light sourceapparatus and, by extension, the projector. At this time, as the fusionvolume of the electrode is increased without interrupting the steadyoperation, it is possible to prevent a brightness of a source light orprojection image from fluctuating after an actual start of use.

The increase of the volume of the fused portion is a phenomenon whichoccurs inside the arc tube. For this reason, it is not necessarily easyto ascertain whether or not the volume of the fused portion is beingincreased. However, it is possible to ascertain the invention as thefollowing aspects of the light source apparatus. Also, the invention canbe realized in aspects, not only as the light source apparatus, but alsoas a drive method of the light source apparatus.

It is also acceptable that the light source apparatus according to someaspects of the invention includes an arc tube having a first electrodeand a second electrode that carry out an emission of light due to adischarge between them, and a drive that, when supplying energy in analternating current to the first electrode and the second electrode,carries out a steady operation supplying a steady energy to the firstelectrode and the second electrode, and an initial operation making acumulative energy supplied to at least one electrode, of the firstelectrode and the second electrode, in an anode period of the relevantelectrode, prior to the steady period, greater than during the steadyperiod. In this way, by making the cumulative energy supplied in theanode period of the at least one electrode greater than at the time ofrated drive, it is possible to increase the temperature of the leadingextremity of the relevant electrode at the time of the initial drive.For this reason, melting and smoothing out the surface of the protrudingleading extremity formed on the leading extremity side of the electrode,and the leading extremity side area on the periphery thereof, utilizingthe lighting start period, it is possible to suppress an occurrence of aflicker and an arc jump.

Also, it is also acceptable that the light source apparatus according tosome aspects of the invention includes an arc tube having a firstelectrode and a second electrode that carry out an emission of light dueto a discharge between them, and a drive that, when supplying energy inan alternating current to the first electrode and the second electrode,carries out a steady operation supplying a steady energy to the firstelectrode and the second electrode, and an initial operation making acumulative energy supplied to at least one electrode, of the firstelectrode and the second electrode, in a latter half of an anode periodof the relevant electrode, prior to the steady period, greater thanduring the steady period. In this way, by making the cumulative energysupplied to the at least one electrode in the latter half of the anodeperiod of the relevant electrode greater than at the time of the rateddrive, it is possible to increase the temperature of the leadingextremity of the relevant electrode at the time of the initial drive.For this reason, melting and smoothing out the surface of the protrudingleading extremity formed on the leading extremity side of the electrode,and the leading extremity side area on the periphery thereof, utilizingthe lighting start period, it is possible to suppress an occurrence of aflicker and an arc jump.

Furthermore, it is also acceptable that the light source apparatusaccording to some aspects of the invention includes an arc tube having afirst electrode and a second electrode that carry out an emission oflight due to a discharge between them, and a drive that, when supplyingan alternating current to the first electrode and the second electrode,carries out a steady operation supplying a steady current to the firstelectrode and the second electrode, and an initial operation making amaximum value of a current supplied in an anode period of at least oneelectrode, of the first electrode and the second electrode, prior to thesteady period, greater than during the steady period. In this way, byincreasing the maximum value of the current supplied in the anode periodof the at least one electrode, it is possible to increase thetemperature of the leading extremity of the relevant electrode at thetime of the initial drive. For this reason, melting and smoothing outthe surface of the protruding leading extremity formed on the leadingextremity side of the electrode, and the leading extremity side area onthe periphery thereof, utilizing the lighting start period, it ispossible to suppress an occurrence of a flicker and an arc jump.

A projector according to an aspect of the invention includes (a) theheretofore described light source apparatus, (b) a light modulatingdevice illuminated by an illumination light from the light sourceapparatus, and (c) a projection optical system that projects an imageformed by the light modulating device.

With the heretofore described projector, as the heretofore describedlight source apparatus is used, a repair or restoration of an electrodeutilizing the lighting start period is possible.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a sectional view illustrating a light source apparatus of oneembodiment of the invention;

FIG. 2 is a block diagram showing a configuration of a current drivedevice embedded in the light source apparatus;

FIG. 3 is an enlarged view illustrating leading extremity peripheralportions of a pair of electrodes;

FIGS. 4A to 4C are enlarged views illustrating a repair of an electrodewith a light source drive device;

FIGS. 5A to 5C are enlarged views illustrating a restoration of anelectrode with the light source drive device;

FIG. 6 is a graph conceptually illustrating one example of an energizedcondition of an arc tube;

FIG. 7 is a graph illustrating a drive waveform at a launching time;

FIG. 8 is a graph conceptually illustrating another example of anenergized condition of the arc tube;

FIG. 9 is a graph illustrating a drive waveform at the launching time;

FIG. 10 is a graph illustrating another drive waveform at the launchingtime;

FIGS. 11A and 11B are graphs illustrating a specific relationshipbetween a drive waveform and a temperature rise;

FIGS. 12A and 12B are graphs illustrating a comparison example of arelationship between a drive waveform and a temperature rise;

FIG. 13A is a diagram schematizing a leading extremity side of anelectrode, and illustrating a flow of heat, while FIG. 13B is a graphshowing a combination type of drive waveform for the electrode;

FIG. 14 is a graph illustrating another drive waveform at the launchingtime;

FIGS. 15A and 15B are graphs illustrating a specific relationshipbetween a drive waveform and a temperature rise;

FIGS. 16A and 16B are graphs illustrating another drive waveform at thelaunching time;

FIGS. 17A and 17B are graphs illustrating a specific relationshipbetween a drive waveform and a temperature rise;

FIGS. 18A and 18B are graphs illustrating a comparison example of arelationship between a drive waveform and a temperature rise;

FIGS. 19A and 19B are graphs illustrating another relationship between adrive waveform and a temperature rise at the launching time;

FIGS. 20A and 20B are graphs illustrating a comparison example of arelationship between a drive waveform and a temperature rise;

FIGS. 21 and 21 are graphs illustrating another relationship between adrive waveform and a temperature rise at the launching time;

FIG. 22 is a flowchart illustrating operations of the light sourceapparatus shown in FIG. 1 etc.;

FIG. 23 is a flowchart illustrating operations of the light sourceapparatus shown in FIG. 1 etc.; and

FIG. 24 is a diagram illustrating a projector in which the light sourceapparatus is embedded.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereafter, with reference to the drawings, a description will be givenof a structure, operations and the like of a light source apparatus,which is one embodiment of the invention.

Light Source Apparatus Structure and Operations

FIG. 1 is a sectional view conceptually illustrating a structure of alight source apparatus 100. In the light source apparatus 100, a lightsource unit 10, which is a discharge lamp, includes a discharge lightemitting type arc tube 1, a reflector 2, which is an elliptical mainreflecting mirror, and a secondary mirror 3, which is a sphericalsecondary reflecting mirror. Also, although a detailed description willbe given hereafter, a light source drive device 70 is an electricalcircuit for supplying an alternating current to the light source unit10, and causing it to emit a light in a desired condition.

In the light source unit 10, the arc tube 1, being configured of aspherically bulging translucent quartz glass tube, a central portion ofwhich bulges in a spherical form, includes a main body portion 11, whichis an enclosed body emitting a light for illumination, and first andsecond sealing portions 13 and 14, which extend along an axis linepassing through both extremities of the main body portion 11.

In a discharge space 12 formed inside the main body portion 11, aleading extremity portion of a tungsten first electrode 15 and, in thesame way, a leading extremity portion of a tungsten second electrode 16,being disposed separated by a predetermined distance, a gas, which is adischarge medium including a noble gas, a metal halogen compound and thelike, is enclosed. Molybdenum metal foils 17 a and 17 b, electricallyconnected to a base portion of the first and second electrodes 15 and 16provided in the main body portion 11, being inserted into an interior ofeach of the sealing portions 13 and 14 extending one at either extremityof the main body portion 11, both sealing portions 13 and 14 are sealedthereby, or by a glass material or the like, airproofed from anexterior. On supplying an alternating pulse form of power, with thelight source drive device 70, to leads 18 a and 18 b connected to themetal foils 17 a and 17 b, an arc discharge occurs between the pair ofelectrodes 15 and 16, and the main body portion 11 emits light at a highluminance.

The secondary mirror 3 is in close proximity to and covers, of the mainbody portion 11 of the arc tube 1, approximately a half of a luminousflux projection forward side, where the second electrode 16 is. Thesecondary mirror 3, being an integrated molded article of quartz glass,includes a secondary reflecting portion 3 a, which returns a luminousflux radiated forward from the main body portion 11 of the arc tube 1 tothe main body portion 11, and a supporting portion 3 b, which is fixedto a perimeter of the second sealing portion 14 in a condition in whichit supports a base portion of the secondary reflecting portion 3 a. Thesupporting portion 3 b, as well as allowing the second sealing portion14 to be inserted through, holds the secondary reflecting portion 3 a ina condition in which it is aligned with the main body portion 11. Thesecondary mirror 3 can be omitted in an application in which a light useefficiency is not considered to be much of a problem.

The reflector 2 is disposed opposed to, of the main body portion 11 ofthe arc tube 1, approximately a half of a luminous flux projection rearside, where the first electrode 15 is. The reflector 2, being anintegrated molded article of crystallized glass or quartz glass,includes a neck-shaped portion 2 a, through which the first sealingportion 13 of the arc tube 1 is inserted, and an elliptically curvedmain reflecting portion 2 b spreading out from the neck-shaped portion 2a. The neck-shaped portion 2 a, as well as allowing the first sealingportion 13 to be inserted through, holds the main reflecting portion 2 bin a condition in which it is aligned with the main body portion 11.

The arc tube 1, as well as being disposed along a system optical axis OAcorresponding to a main reflecting portion 2 b rotational symmetry axisor optical axis, is disposed in such a way that an emission center O ofthe first and second electrodes 15 and 16 inside the main body portion11 corresponds to a first focal point F1 position on an ellipticalsurface of the main reflecting portion 2 b. When lighting the arc tube1, luminous fluxes radiated from an arc in a periphery of the emissioncenter O of the main body portion 11 are reflected by the mainreflecting portion 2 b, or are further reflected by the main reflectingportion 2 b after a reflection by the secondary reflecting portion 3 a,and become luminous fluxes converged at a second focal point F2 positionon the elliptical surface. That is, the reflector 2 and the secondarymirror 3 having reflecting surfaces which are approximately axisymmetricwith respect to the system optical axis OA, the pair of electrodes 15and 16 are disposed in such a way that an electrode axis, which is anaxial center thereof, is caused to approximately correspond to thesystem optical axis OA.

The arc tube 1 is made by means of a shrink sealing which, holding thefirst and second electrodes 15 and 16 fixed to a leading extremity ofthe metal foils 17 a and 17 b in, for example, the quartz glass tube,and heating the quartz glass tube from a perimeter, with a burner, inportions corresponding to both sealing portions 13 and 14, causes asoftening and a contraction. The arc tube 1, in a condition in which thefirst sealing portion 13 is inserted in the neck-shaped portion 2 a ofthe reflector 2, is fixed by injecting and filling with an inorganicadhesive C, and allowing it to solidify, and the secondary mirror 3, ina condition in which the second sealing portion 14 of the arc tube 1 isinserted through the supporting portion 3 b, is fixed by injecting andfilling with the inorganic adhesive C, and allowing it to solidify.

FIG. 2 is a block diagram schematically showing a configuration of thelight source drive device 70 for causing the light source unit 10 shownin FIG. 1 to operate illuminated in a desired condition.

The light source drive device 70, as well as generating an alternatingcurrent for carrying out a discharge between the pair of electrodes 15and 16 shown in FIG. 1 etc., controls a condition of a supply of thealternating current to both the electrodes 15 and 16. The light sourcedrive device 70 includes a lighting device 70 a, a controller 70 b, anda DC/DC converter 70 c. Herein, as one example, a description will begiven of a case in which the light source drive device 70 uses anexternal power source. That is, the light source drive device 70 beingconnected to an AC/DC converter 81, the AC/DC converter 81 is connectedto a commercial power source 90. The AC/DC converter 81 converts analternating current supplied from the commercial power source 90 into adirect current.

The lighting device 70 a is a circuit portion which illuminates anddrives the light source unit 10 of FIG. 1. A drive waveform output fromthe light source drive device 70 is adjusted by the lighting device 70a. Herein, the drive waveform having as elements an output current orvoltage frequency, an amplitude, a duty ratio, a positive and negativeamplitude ratio, a waveform characteristic, and the like, a drivecurrent which has an optional waveform characteristic, such as, forexample, a rectangular wave, a triangular wave, or a wave in which theyare superimposed, is output from the lighting device 70 a to the lightsource unit 10.

The controller 70 b being a circuit unit configured of, for example, amicrocomputer, a memory, a sensor, an interface and the like, it isdriven by an appropriate drive voltage generated by the DC/DC converter70 c, which is a power source. The controller 70 b includes a drivecontrol portion 74, which controls an operational condition of thelighting device 70 a, an evaluating portion 75, which evaluates acondition of the arc tube 1, and a data storage portion 76, which storesvarious kinds of information such as an operational aspect of thelighting device 70 a, that is, a power supply condition. Also, thecontroller 70 b includes a timer 77, for measuring a cumulative lit timeof the arc tube 1, and a voltage sensor 78, which detects a voltageapplied to the arc tube 1.

The drive control portion 74 is a portion which operates in accordancewith a program stored in the data storage portion 76 or the like. Thedrive control portion 74, in a regular operation, as well as selecting,from initial operation power supply conditions and steady operationpower supply conditions stored in the data storage portion 76, oneappropriate to a current condition of the arc tube 1, causes thelighting device 70 a to carry out an initial operation or a steadyoperation in accordance with the selected power supply condition. Thedrive control portion 74, in conjunction with the lighting device 70 a,functions as a drive portion for supplying power to the arc tube 1, andcausing it to carry out a necessary lighting operation. In theembodiment, an operation supplying a steady energy to the firstelectrode 15 and the second electrode 16 is taken to be the steadyoperation, and an operation supplying energy to the first electrode 15and the second electrode 16 before carrying out the steady operation, inan operation differing from the steady operation, is taken to be theinitial operation.

The evaluating portion 75 is a portion which evaluates what level thecumulative lit time of the arc tube 1 is at, and what level the voltageapplied to the arc tube 1 is at. Specifically, it evaluates what stageof arc tube 1 aging stages the cumulative lit time of the arc tube 1corresponds to, and what stage of the arc tube 1 aging stages thevoltage applied to the arc tube 1 corresponds to.

The data storage portion 76, apart from the operational program of thedrive control portion 74, and the like, stores a plurality of initialpower supply conditions as aspects of the initial operation of the arctube 1, and stores a plurality of steady power supply conditions asaspects of the steady operation of the arc tube 1. Two or more initialdrive power supply conditions being included in the former initial powersupply conditions, one or more steady drive power supply conditions areincluded in the latter steady power supply conditions. Specifically, thedata storage portion 76 stores various kinds of parameter, such as acurrent value at a starting time or launching time included in theinitial operation, a setting value of a frequency and the like, anincrease rate, an increase timing, an anode duty ratio, a direct currentsuperposition amount, and various kinds of waveform to be superimposedon the rectangular wave. Also, the data storage portion 76 stores acurrent value, a frequency, a triangular wave jump rate, and the like,of the steady operation at a rated drive. Herein, the triangular wavejump rate indicates a proportion of a maximum current value with respectto an average current value, in a half cycle of the superimposed wave inwhich the triangular wave is superimposed on the rectangular wave.

The timer 77, checking the lit time of the arc tube 1, holds thecumulative lit time, which is an accumulation of a lit time for everyoccasion. The voltage sensor 78 detects and holds the voltage applied tothe first and second electrodes 15 and 16 of the arc tube 1 via thelighting device 70 a.

FIG. 3 is an enlarged view of the leading extremity portions of thefirst and second electrodes 15 and 16 enclosed inside the arc tube 1.The first and second electrodes 15 and 16 respectively include leadingextremities 15 a and 16 a, main bodies 15 b and 16 b, coils 15 c and 16c, and core rods 15 d and 16 d. By providing the glob shaped main bodies15 b and 16 b at leading extremity sides of the first and secondelectrodes 15 and 16, it is possible to increase a heat capacity. Theleading extremity portions of the first and second electrodes 15 and 16are formed at, for example, a stage before enclosing, by wrappingtungsten around the core rods 15 d and 16 d, and heating and fusingthem. At this time, a remaining portion of the wrapped tungsten, whichhas not been fused, becomes the coil rods 15 c and 16 c.

FIGS. 4A to 4C are conceptual diagrams illustrating an action on thefirst electrode 15 at a time of a fusing drive on, of the two electrodes15 and 16, the first electrode 15.

In the case of the first electrode 15 shown in FIG. 4A, a plurality ofconcavities and convexities 61 occur irregularly in a leading extremityside area 15 g on a perimeter of the leading extremity 15 a. Also, aplurality of microscopic concavities and convexities 63 also occur,along with a continued use, on a surface of the leading extremity 15 a.In this case, a phenomenon of a discharge origin moving between theleading extremity 15 a and the concavities and convexities 61 and 63,that is, a flicker or arc jump, occurs. Herein, the flicker refers tothe movement of the discharge origin occurring continuously, while thearc jump refers to the discharge origin moving completely from anoriginal discharge origin position. The flicker and the arc jump cause aflickering screen or an illuminance reduction. When carrying out thefusing drive on at least the first electrode 15 at the launching time,during the initial operation of the arc tube 1, surfaces of these kindsof concavities and convexities 61 and 63 are melted by raising atemperature of the leading extremity side of the first electrode 15, anda fused portion 64 is formed, as shown in FIG. 4B. That is, by a fusingdrive appropriate to the current condition of the arc tube 1 beingselected, and an energizing operation being carried out, at thelaunching time by the light source drive device 70, the temperature ofthe leading extremity 15 a and the like rises. The fusing drive carriedout here being a comparatively low level fusing drive, it is possible tosecure an appropriate temperature rise of the leading extremity 15 a andthe leading extremity side area 15 g. By this means, it being possibleto form the fused portion 64 with the leading extremity 15 a left almostintact, it is possible to smooth out the concavities and convexities 61and 63. At this time, a volume of the fused portion 64 of the leadingextremity side of the first electrode 15 is larger than a volume of afused portion of the leading extremity side of the first electrode 15 ata time of the rated drive during the steady operation, to be describedhereafter. Although details will be omitted, a surface of the leadingextremity 16 a of the second electrode 16 opposing the first electrode15 is also fused but, in this case, an energizing operation of a regularinitial drive being carried out on the second electrode 16 without afusing drive being carried out, the volume of the fused portion issmall, and of an extent that a shape does not change. As the heretoforedescribed fusing drive is carried out during the initial operation, itdoes not have a large effect on a performance as a video instrument.

After the operation according to the heretofore described kind of fusingdrive, the initial operation is finished, and a shift is made to thesteady operation. In the steady operation, the rated drive is carriedout and, as shown in FIG. 4C, the shape of the electrode leadingextremity 15 a is maintained.

The description given heretofore has been of the first electrode 15 but,with regard to the second electrode 16 too, as the same kinds ofconcavities and convexities 61 and 63 are formed with time, it ispossible to smooth out the concavities and convexities 61 and 63 bycausing an energizing operation with the same kind of fusing drive asthat heretofore described.

Also, in the event that an energizing time of the first and secondelectrodes 15 and 16 becomes long, despite the two electrodes 15 and 16wearing away and the smoothing out of the concavities and convexities 61and 63 becoming necessary, the concavities and convexities 61 and 63gradually become difficult to fuse. Therein, with an operation of thelight source drive device 70, an amount of a temperature rise of theleading extremity sides of the first and second electrodes 15 and 16 atthe launching time, during the initial operation of the arc tube 1, is,for example, gradually increased along with an increase in thecumulative lit time. By this means, as it is possible to secure a fusedamount of the concavities and convexities 61 and 63 even when the littime becomes long, it is possible to prevent any impediment tomaintaining the shapes of the leading extremities 15 a and 16 a. Herein,as a method of increasing the amount of the temperature rise of theleading extremity sides of the electrodes 15 and 16, for example, (1) anincrease of an increase rate of a current supplied to the two electrodes15 and 16 in at least, during the initial operation, a launching periodincluding a period immediately before switching to the steady operation,(2) an increase of a current setting value at a termination of thelaunching period provided after a commencement of the initial operation,(3) an increase of the anode duty ratio relating to a subject electrode,of the two electrodes 15 and 16, at the time of the initial operation,(4) an increase of the direct current superposition amount with respectto an alternating current at the time of the initial operation, (5) anadjustment of a superposition proportion of each kind of waveform to besuperimposed on the rectangular wave at the time of the initialoperation, (6) a reduction of the frequency of the current supplied tothe two electrodes 15 and 16 at the time of the initial operation, andthe like, can be considered. The heretofore described methods (1) to (6)are enabled by making a cumulative energy supplied in an anode period ofeach electrode 15 and 16 at the time of the fusing drive of the initialoperation greater than a cumulative energy supplied in an anode periodof the corresponding electrodes 15 and 16 at the time of the rated driveduring the steady operation. Also, the heretofore described methods (1)to (6) are enabled by making a cumulative energy supplied in a latterhalf of the anode period of each electrode 15 and 16 at the time of thefusing drive of the initial operation greater than a cumulative energysupplied in a latter half of the anode period of the correspondingelectrodes 15 and 16 in the rated drive of the steady operation. Also,the heretofore described methods (1) to (6) are enabled by making amaximum value of a current supplied in the anode period of eachelectrode 15 and 16 at the time of the fusing drive of the initialoperation greater than a maximum value of a current supplied in theanode period of the corresponding electrodes 15 and 16 in the rateddrive of the steady operation.

FIGS. 5A to 5C are conceptual diagrams illustrating a restorativeoperation on, of the two electrodes 15 and 16, the first electrode 15.

In the case of the first electrode 15 shown in FIG. 5A, the cumulativelit time has increased, the aging has progressed, and it is in a seriousaging condition wherein restoration is necessary. Specifically, in theleading extremity side area 15 g of the main body 15 b, a condition issuch that a plurality of concavities and convexities 65, of a sizecomparable with the leading extremity 15 a, have appeared irregularly.In this case too, the phenomenon of the discharge origin moving betweenthe leading extremity 15 a and the concavities and convexities 65, thatis, the arc jump or the flicker, occurs. In the case of reaching thecondition in which the aging of the first electrode 15 has progressed inthis way, by selecting and executing a fusing drive shown in FIG. 5B anda reproduction drive shown in FIG. 5C, it is possible to return thefirst electrode 15 to a condition close to the condition before theaging.

Specifically, as shown in FIG. 5B, by the energizing operation beingcarried out with the fusing drive, by the light source drive device 70,at the time of the initial operation, the temperature of the leadingextremity 15 a and the like of the first electrode 15 rises. That is,the first electrode 15 on which have occurred the concavities andconvexities 65, which cause the flicker and arc jump, is heated as faras or higher than the case of the regular initial drive or thecomparatively low level fusing drive shown in FIG. 4B. The fusing drivecarried out here being a comparatively high level fusing drivecorresponding to a special operation, it can melt and smooth out theconcavities and convexities 65 and the leading extremity 15 a of thefirst electrode 15, forming a fused portion 62 which spreads out flat.As the heretofore described fusing drive is carried out during theinitial operation, it does not have a large effect on the performance asa video instrument. In the case of carrying out the comparatively highlevel fusing drive in the initial operation, the reproduction drivewhich causes the leading extremity 15 a to grow is carried out in thesteady operation. With the reproduction drive of the steady operation,as shown in FIG. 5C, it is possible to cause a well-shaped leadingextremity 15 a to grow from a center of the flat fused portion 62 ofFIG. 5B by an adjustment of the drive waveform supplied to the arc tube1. That is, at the time of the steady operation, rather than the rateddrive corresponding to the regular operation, the reproduction drivecorresponding to the special operation is selected and carried out bythe light source drive device 70. With the reproduction drive, it ispossible to cause a regrowth of a leading extremity 15 a which has acomparatively good shape and is of a sufficient size. The heretoforedescribed reproduction drive being a process which causes the leadingextremity 15 a to grow large, as it can be presumed that a luminance ofthe light source unit 10 gradually increases, and a brightness of aprojection image increases, along with a gradual decrease of an arclength, there is little likelihood of a user noticing a progression ofthe restorative operation, and it is possible to prevent an aging of adisplay performance from a visual aspect wherein a display operation ofa video instrument fluctuates violently along with the restoration.

The description given heretofore has been of the first electrode 15 but,with regard to the second electrode 16 too, as the same kinds ofconcavities and convexities 65 are formed with time, it is possible to,as well as melting and smoothing out the concavities and convexities 65and a leading extremity 16 a by causing an energizing operation with thesame kind of comparatively high level fusing drive corresponding to aspecial operation as that heretofore described, cause a regrowth of theleading extremity 16 a which has a comparatively good shape and is of asufficient size by causing an energizing operation in the steadyoperation with the same kind of special operation reproduction drive asthat heretofore described.

Also, in the event that the energizing time of the first and secondelectrodes 15 and 16 becomes long, despite the two electrodes 15 and 16wearing away and the smoothing out of the concavities and convexities 65becoming necessary, the concavities and convexities 65 formed on theleading extremities 15 a and 16 a gradually become difficult to fuse.Therein, with an operation of the light source drive device 70, theamount of the temperature rise of the leading extremity sides of thefirst and second electrodes 15 and 16 in the initial operation of thearc tube 1, is, for example, gradually increased along with the increasein the cumulative lit time. By this means, as it is possible to secure afused amount of the concavities and convexities 65 even when the littime of the arc tube 1 becomes long, it is possible to prevent anyimpediment to a good growth of the leading extremities 15 a and 16 a.Herein, as a method of increasing the amount of the temperature rise ofthe leading extremity sides of the electrodes 15 and 16, for example,(1) an increase of the increase rate of the current supplied to the twoelectrodes 15 and 16 in at least, during the initial operation, thelaunching period including the period immediately before switching tothe steady operation, (2) an increase of the current setting value atthe termination of the launching period provided after the commencementof the initial operation, (3) an increase of the anode duty ratiorelating to the subject electrode, of the two electrodes 15 and 16, atthe time of the initial operation, (4) an increase of the superpositionamount of the direct current of the initial operation to the twoelectrodes 15 and 16, (5) an adjustment of the superposition proportionof each kind of waveform to be superimposed on the rectangular wave ofthe initial operation, (6) a reduction of the frequency of the currentsupplied to the two electrodes 15 and 16 at the time of the initialoperation, and the like, can be considered. The heretofore describedmethods are similar to the low level fusing drive shown in FIGS. 4A to4C but, in order that the volume of the fused portion of the leadingextremity side of the electrode due to the high level fusing drive isgreater than the volume of the fused portion of the leading extremityside of the electrode due to the low level fusing drive, the energysupplied to the electrodes at the time of the fusing drive isappropriately adjusted.

In the present specification, the cumulative energy being a temporalintegration value of an input energy P1 (to be described hereafter)flowing into the electrodes within a predetermined period, it increasesalong with an increase of the current value or the anode period. Also,as will be described hereafter, the input energy P1 during the anodeperiod is a value in which the drive waveform (the current) ismultiplied by a coefficient α, which is an input energy per unitarycurrent. The coefficient α is determined by the condition of theelectrodes, a pressure inside the arc tube 1, or the operationalcondition or the like of the arc tube 1. For this reason, in theembodiment, the cumulative energy is adjusted by adjusting the currentvalue in the anode period, or a length of the anode period.

FIRST OPERATIONAL EXAMPLE

Hereafter, a description will be given of a first operational examplewith the fusing drive of the light source apparatus 100 shown in FIG. 1.FIG. 6 is a graph conceptually illustrating the energizing condition bythe light source drive device 70 from the initial operation to thesteady operation of the arc tube 1, in the operational example. In thegraph, a horizontal axis indicates a time elapsed since a start oflighting, while a vertical axis indicates the voltage (a chain line),the power (a broken line), and the current (a solid line) which aresupplied to the arc tube 1. In the graph, the energizing operation ofthe regular initial drive is indicated in the graph by a two-dot chainline.

In the first operational example, an initial operation period of aroundsixty-something seconds is provided, after which a steady operationperiod is provided. The initial operation period being a period forsupplying a transient energy (specifically, a transient power) to thearc tube 1, the steady operation period is a period for supplying asteady energy (specifically, a steady power) to the arc tube 1. In thiscase, with regard to the initial operation period, a starting period ofaround a few seconds, and a subsequent launching period of around 60seconds, are provided. Regarding the voltage, it gradually increasesduring the initial operation period, and saturates at a certain valueduring the steady operation period. Also, regarding the power, itgradually increases in the launching period during the initial operationperiod, and during the steady operation period it is normally set by arated operation by which it is maintained at a constant value.Furthermore, regarding the current, it gradually increases by a certainproportion in the launching period during the initial operation periodafter a dielectric breakdown (an area A1 in the figure), temporarilydecreases at a subsequent starting time of the steady operation (an areaA2 in the figure), and is maintained at an approximately constant valueduring the subsequent steady operation period (an area A3 in thefigure).

In this case, by increasing the value of the current supplied to thefirst and second electrodes 15 and 16 along with the passing of time inthe area A1 of at least, during the initial operation, the launchingperiod including the period immediately before switching to the steadyoperation, the temperature of the first and second electrodes 15 and 16gradually increases, and it is possible, in a final stage of thelaunching period, to increase the volume of the fused portions 62 and 64of the leading extremity sides of the first and second electrodes 15 and16 in comparison with the time of the rated drive during the steadyoperation. Also, although an illustration is omitted, in the case of thehigh level fusing drive shown in FIG. 5B, the fusion volume is increasedin comparison with the low level fusing drive shown in FIG. 4B byappropriately making a gradient of the current increase relativelysteeper.

The description given heretofore has been one in which the volumes ofthe fused portions 62 and 64 are increased for both the first and secondelectrodes 15 and 16, but it is possible to increase the volumes of thefused portions 62 and 64 for only either one of the first electrode 15or the second electrode 16. In this case, as shown in FIG. 7, thealternating current supplied to the arc tube 1, only on, for example, aside on which the first electrode 15 becomes the anode, graduallyincreases as in any one of L11 to L13 shown in FIG. 6, and is maintainedat a value B0 of the regular operation indicated by the two-dot chainline in FIG. 6 on a side on which the second electrode 16 becomes theanode. In the case in which the fusing drive is carried out for onlyeither one of the first electrode 15 or the second electrode 16 in thisway, the first electrode 15 and the second electrode 16 are alternatelymade a main fusion subject by carrying out a fusing drive increasing thevolumes of the fused portions 62 and 64 of the leading extremity sidesof the second electrode 16 as the fusing drive of the current initialoperation, in the event that a fusing drive increasing the volumes ofthe fused portions 62 and 64 of the leading extremity sides of the firstelectrode 15 has been carried out in an immediately preceding initialoperation, and carrying out a fusing drive increasing the volumes of thefused portions 62 and 64 of the leading extremity sides of the firstelectrode 15 as the fusing drive of the current initial operation, inthe event that a fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the secondelectrode 16 has been carried out as the fusing drive of the immediatelypreceding initial operation.

Also, taking into consideration that in the event that the energizingtime of the first and second electrodes 15 and 16 becomes long, and theaging of the arc tube 1 progresses, the concavities and convexities 61,63 and 65 formed on the leading extremities 15 a and 16 a graduallybecome difficult to fuse, it is possible to gradually increase thecurrent increase rate along with the increase of the cumulative littime. As shown in the graph of FIG. 6, in the area A1, as thecharacteristic L11 of the current to the first and second electrodes 15and 16 corresponds to the low level fusing drive when the aging of thearc tube 1 is in the initial stage, the current increase rate (thegradient) is at its smallest. Also, as the current characteristic L12corresponds to the low level fusing drive when the aging of the arc tube1 has progressed to some degree, the current increase rate (thegradient) has become a little larger and, as the current characteristicL13 corresponds to the low level fusing drive when the aging of the arctube 1 has further progressed, the current increase rate (the gradient)has become still larger. According to the above, as the operation of thelow level fusing drive is set in accordance with the aging stage of thearc tube 1, so that an amount of energy is supplied sufficient to securethe fusion volumes of the leading extremity sides of the electrodes 15and 16, which have become difficult to fuse due to the aging of the arctube 1 progressing, an initial operation is carried out which is inaccordance with the extent of the aging of the arc tube 1.

Heretofore, to facilitate the description, it has been taken that theregular rated drive is carried out during the steady operation period,that is, in the area A3, but it is possible, when necessary, to carryout the reproduction drive (refer to FIG. 5C) in the area A3.

SECOND OPERATIONAL EXAMPLE

Hereafter, a description will be given of a second operational examplewith the fusing drive. FIG. 8 is a graph conceptually illustrating theenergizing condition by the light source drive device 70 from theinitial operation to the steady operation of the arc tube 1, in theoperational example.

In the second operational example too, the initial operation period ofaround sixty-something seconds is provided, after which the steadyoperation period is provided. In this case, the current is maintained ata comparatively large constant value from the commencement to amid-point during the initial operation period after the dielectricbreakdown (an area A1 in the figure), temporarily increases to a peakform at a subsequent termination of the launching time (an area A2 inthe figure), and is maintained at an approximately constant value duringthe subsequent steady operation period (an area A3 in the figure). Atiming of increasing the current supplied to the first and secondelectrodes 15 and 16 can be arranged to be a time at which, for example,the value of the voltage between the first and second electrodes 15 and16 reaches a predetermined value, but it can also be arranged to be atime at which a predetermined time elapses from the lighting, that is, astarting time of the initial operation.

In this case, in the area A2 of the final stage of the initialoperation, which is the termination of the launching operation, as thevalue of the current supplied to the first and second electrodes 15 and16 is temporarily sharply increased, the temperature of the first andsecond electrodes 15 and 16 temporarily increases, and it is possible toincrease the volume of the fused portions 62 and 64 of the leadingextremity sides of the first and second electrodes 15 and 16 incomparison with the time of the rated drive during the steady operation.Although an illustration is omitted, in the case of the fusing driveshown in FIG. 5B, the fusion volume is increased in comparison with thefusing drive shown in FIG. 4B by appropriately making the amount of thecurrent increase relatively larger.

The description given heretofore has been one in which the volumes ofthe fused portions 62 and 64 are increased for both the first and secondelectrodes 15 and 16, but it is possible to increase the volumes of thefused portions 62 and 64 for only either one of the first electrode 15or the second electrode 16. In this case, as shown in FIG. 9, thealternating current supplied to the arc tube 1, increasing only on, forexample, the side on which the first electrode 15 becomes the anode, ismaintained at the value B0 of the regular operation on the side on whichthe second electrode 16 becomes the anode. In the case in which thefusing drive is carried out for only either one of the first electrode15 or the second electrode 16 in this way, the first electrode 15 andthe second electrode 16 are alternately made the main fusion subject bycarrying out the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the secondelectrode 16 as the fusing drive of the current initial operation, inthe event that the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the first electrode15 has been carried out in the immediately preceding initial operation,and carrying out the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the first electrode15 as the fusing drive of the current initial operation, in the eventthat the fusing drive increasing the volumes of the fused portions 62and 64 of the leading extremity sides of the second electrode 16 hasbeen carried out as the fusing drive of the immediately precedinginitial operation.

Also, taking into consideration that in the event that the energizingtime of the first and second electrodes 15 and 16 becomes long, and theaging of the arc tube 1 progresses, the concavities and convexities 61,63 and 65 formed on the leading extremities 15 a and 16 a graduallybecome difficult to fuse, it is possible to gradually increase a peakvalue of the current value along with the increase of the cumulative littime. As shown in the graph of FIG. 8, in the area A2, as acharacteristic L21 of the current to the first and second electrodes 15and 16 corresponds to the low level fusing drive when the aging of thearc tube 1 is in the initial stage, a peak time current value is at itssmallest. Also, as a current characteristic L22 corresponds to the lowlevel fusing drive when the aging of the arc tube 1 has progressed tosome degree, the peak time current value has become a little larger and,as a current characteristic L23 corresponds to the low level fusingdrive when the aging of the arc tube 1 has further progressed, the peaktime current value has become still larger. According to the above, asthe operation of the low level fusing drive is set in accordance withthe aging stage of the arc tube 1, so that the amount of energy issupplied sufficient to secure the fusion volumes of the leadingextremity sides of the electrodes 15 and 16, which have become difficultto fuse due to the aging progressing, an initial operation is carriedout which is in accordance with the extent of the aging of the arc tube1.

Heretofore, to facilitate the description, it has been taken that theregular rated drive is carried out during the steady operation period,that is, in the area A3, but it is possible, when necessary, to carryout the reproduction drive in the area A3.

THIRD OPERATIONAL EXAMPLE

Hereafter, a description will be given of a third operational examplewith the fusing drive. FIG. 10 is a graph conceptually illustrating theinitial operation of the arc tube 1, in the operational example. In thegraph, a horizontal axis indicates the time, while a vertical axisindicates the current value. Also, a solid line indicates the regularinitial drive initial operation, while current characteristics L31 andL33 of a dotted line and a chain line indicate the initial operation ofthe fusing drive. In the case of the third operational example, duringthe launching period of the fusing drive, the anode duty ratio of thefirst electrode 15 is increased relatively compared with the anode dutyratio of the first electrode 15 in the rated drive. With this kind ofdrive waveform, as well as it being possible to make the cumulativeenergy supplied in the anode period of the first electrode 15 at thetime of the fusing drive greater than the cumulative energy supplied inthe anode period of the first electrode 15 at the time of the rateddrive, it is possible to make the cumulative energy supplied in thelatter half of the anode period of the first electrode 15 at the time ofthe fusing drive greater than the cumulative energy supplied in thelatter half of the anode period of the first electrode 15 at the time ofthe rated drive, and it is possible to reliably increase the volumes ofthe fused portions 62 and 64 of the leading extremity sides of the firstelectrode 15 in comparison with the time of the rated drive during thesteady operation. As the current characteristic L31 of the dotted linecorresponds to the low level fusing drive for the electrode which hasbecome a little difficult to fuse when the aging of the arc tube 1 is atthe initial stage, the current characteristic L33 of the chain linecorresponds to the low level fusing drive for the electrode which hasbecome considerably difficult to fuse when the aging of the arc tube 1has further progressed.

The description given heretofore has been one in which the volumes ofthe fused portions 62 and 64 are increased for only the first electrode15 but, simply by inverting a polarity of the drive waveform, it is alsopossible to increase the volumes of the fused portions 62 and 64 foronly the second electrode 16. Also, when repeating the initial operationand the steady operation for a plurality of cycles, it is possible toalternately increase the volumes of the fused portions 62 and 64 of theleading extremity sides of the two electrodes 15 and 16 by alternatelyincreasing the anode duty ratio during the launching period for thefirst and second electrodes 15 and 16, by a unit of each initialoperation. Alternatively, in the case of carrying out the fusing drivefor only either one of the first electrode 15 or the second electrode16, by the unit of each initial operation, the first electrode 15 andthe second electrode 16 are alternately made the main fusion subject bycarrying out the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the secondelectrode 16 as the fusing drive of the current initial operation, inthe event that the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the first electrode15 has been carried out in the immediately preceding initial operation,and carrying out the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the first electrode15 as the fusing drive of the current initial operation, in the eventthat the fusing drive increasing the volumes of the fused portions 62and 64 of the leading extremity sides of the second electrode 16 hasbeen carried out as the fusing drive of the immediately precedinginitial operation.

FIGS. 11A and 11B are graphs specifically illustrating an advantage ofincreasing the anode duty ratio in the fusing drive. FIG. 11A shows oneexample of a drive waveform, in the same way as FIG. 10, while FIG. 11Bshows the temperature of the leading extremity 15 a of the firstelectrode 15. In FIG. 11A, a horizontal axis shows the time, and avertical axis shows the current. In this case, the frequency of thedrive waveform is taken to be 100 Hz, and the anode duty ratio of thefirst electrode 15 is taken to be 60%. Also, an average power is 170 W.In FIG. 11B, a horizontal axis shows the time, and a vertical axis showsthe temperature. Also, a solid line in the graph indicates a simulatedtemperature of the protruding leading extremity 15 a, a dotted lineindicates a one cycle average temperature of the leading extremity 15 a,and a chain line indicates an average temperature in the anode period ofthe leading extremity 15 a.

Meanwhile, FIG. 12A, being a graph for a comparison, shows one exampleof a drive waveform at the time of the rated drive of the steadyoperation, while FIG. 12B shows the temperature of the leading extremity15 a of the first electrode 15 in a case of using the drive waveform ofFIG. 12A. In this case, as can be understood from FIG. 12A, the anodeduty ratio of the first electrode 1S is taken to be 50%. Also, in FIG.12B, in the same way as in FIG. 11B, a solid line in the graph indicatesthe simulated temperature of the protruding leading extremity 15 a, adotted line indicates the one cycle average temperature of the leadingextremity 15 a, and a chain line indicates the average temperature inthe anode period of the leading extremity 15 a. As is clear whencomparing FIG. 12B and FIG. 11B, it can be understood that, comparedwith the case of making the anode duty ratio 50%, in the case of makingthe anode duty ratio of the first electrode 15 60%, as the temperatureat the leading extremity 15 a anode time (a peak value and an averagevalue) and the one cycle average temperature of the leading extremity 15a rise, there is more likelihood of increasing the volumes of theleading extremity 15 a and the fused portions 62 and 64 in a peripherythereof.

Hereafter, a description will be given of a specific method ofcalculating the simulation of the temperature rise shown in FIGS. 11Band 12B.

FIG. 13A is a figure schematizing the leading extremity side of thefirst electrode 15, and illustrating a flow of heat. The input energy P1flowing into the leading extremity 15 a of the first electrode 15 eachunit time, it flows out into the main body 15 b, via a contact area S ofa boundary 15 h, as a transmitted energy P2. Herein, the input energy P1being one, among energies supplied to the first electrode 15, whichbecomes a heat energy, the transmitted energy P2 is an energy which isheat transferred from the leading extremity 15 a to the main body 15 b.The input energy P1, being of a value linked to the drive waveformsupplied to the arc tube 1, changes with time in the same way as thedrive waveform. For example, the input energy P1 when the firstelectrode 15 is the anode being one wherein the drive waveform in theanode period is multiplied by the coefficient α, the input energy P1when the first electrode 15 is the cathode can be made one wherein thedrive waveform in the anode period is multiplied by a coefficient β.Also, the transmitted energy P2 is a flow of heat generated by adifference in temperature between the leading extremity 15 a and themain body 15 b.

FIG. 13B is a graph showing a combination type of drive waveform for thefirst electrode 15. As shown in the figure, a cycle of the drivewaveform being P, one cycle is thought of as being divided into unittimes Δt which are, for example, around one thirtieth Herein, focusingattention on an n^(th) division, in order to consider a movement of heatin the leading extremity 15 a, the temperature of the leading extremity15 a at a starting point of the division is taken to be Tn, and thetemperature of the leading extremity 15 a at a finishing point of thedivision is taken to be Tn+1. Herein, taking the input energy in then^(th) division to be P1 n, and the transmitted energy in the n^(th)division to be P2 n, as a total amount of energy flowing into theleading extremity 15 a is P1 n×Δt, and a total amount of energy flowingout of the leading extremity 15 a is P2 n×Δt, a total amount of energyaccumulated in the leading extremity 15 a is (P1 n-P2 n)×Δt. Herein,taking a heat capacity of the leading extremity 15 a to be C, atemperature change ΔTn of the leading extremity 15 a due to theaccumulated amount of heat isΔTn=(P1n−P2n)×Δt/C  (1).Therefore,Tn+1=Tn+ΔTn=Tn+(P1n−P2n)×Δt/C  (2),so it is possible to calculate the temperature rise in each division.When actually calculating the temperature, T1 is fixed at an appropriatevalue, and the temperature rises are calculated in an order of T1, T2,T3, . . . from the heretofore described equations (1) and (2). Also,when calculating the transmitted energy P2, as well as considering thecontact area S and a heat conduction rate X, a temperature of the mainbody 15 b is fixed at an appropriate value as a border condition. Whencalculating the temperatures of FIGS. 11A and 11, the temperature of themain body 15 b is taken to be 3,500K. According to the above, it ispossible to calculate a temperature change characteristic of one cycleof the leading extremity 15 a. The temperature change characteristicchanging in accordance with a pattern of the drive waveform, it ispossible to relatively compare temperature change conditions of eachdrive waveform pattern.

FOURTH OPERATIONAL EXAMPLE

Hereafter, a description will be given of a fourth operational examplewith the fusing drive. FIG. 14 is a graph conceptually illustrating theinitial operation of the arc tube 1, in the operational example. In thegraph, a horizontal axis indicates the time, while a vertical axisindicates the current value. Also, a solid line indicates the regularinitial drive initial operation, while current characteristics L41 andL43 of a dotted line and a chain line indicate the initial operation ofthe fusing drive. In the case of the fourth operational example, duringthe launching period of the fusing drive, the value of the current tothe first electrode 15 is increased from C0 to C1 and C2 bysuperimposing the direct current. Together with this, the value of thecurrent to the second electrode 16 is reduced to 2C0-C1 and 2C0-C2. Withthis kind of drive waveform, as well as it being possible to make thecumulative energy supplied in the anode period of the first electrode 15at the time of the fusing drive greater than the cumulative energysupplied in the anode period of the first electrode 15 at the time ofthe rated drive, it is possible to make the cumulative energy suppliedin the latter half of the anode period of the first electrode 15 at thetime of the fusing drive greater than the cumulative energy supplied inthe latter half of the anode period of the first electrode 15 at thetime of the rated drive, and furthermore, it is possible to make themaximum value of the current supplied in the anode period of the firstelectrode 15 at the time of the fusing drive greater than the maximumvalue of the current supplied in the anode period of the first electrode15 at the time of the rated drive during the steady operation. By thismeans, it is possible to reliably increase the volumes of the fusedportions 62 and 64 of the leading extremity sides of the first electrode15 in comparison with the time of the rated drive during the steadyoperation. As the current characteristic L41 of the dotted linecorresponds to the low level fusing drive for the electrode which hasbecome a little difficult to fuse when the aging of the arc tube 1 hasprogressed to a certain extent, the current characteristic L43 of thechain line corresponds to the low level fusing drive for the electrodewhich has become considerably difficult to fuse when the aging of thearc tube 1 has further progressed.

The description given heretofore has been one in which the volumes ofthe fused portions 62 and 64 are increased for only the first electrode15 but, simply by inverting the polarity of the drive waveform, it isalso possible to increase the volumes of the fused portions 62 and 64for the second electrode 16. Also, when repeating the initial operationand the steady operation for a plurality of cycles, it is possible toalternately increase the volumes of the fused portions 62 and 64 of theleading extremity sides of the two electrodes 15 and 16 by alternatelychanging a polarity of the direct current superimposed during thelaunching period for the first and second electrodes 15 and 16, by aunit of each initial operation. Alternatively, in the case of carryingout the fusing drive for only either one of the first electrode 15 orthe second electrode 16, by the unit of each initial operation, thefirst electrode 15 and the second electrode 16 are alternately made themain fusion subject by carrying out the fusing drive increasing thevolumes of the fused portions 62 and 64 of the leading extremity sidesof the second electrode 16 as the fusing drive of the current initialoperation, in the event that the fusing drive increasing the volumes ofthe fused portions 62 and 64 of the leading extremity sides of the firstelectrode 15 has been carried out in the immediately preceding initialoperation, and carrying out the fusing drive increasing the volumes ofthe fused portions 62 and 64 of the leading extremity sides of the firstelectrode 15 as the fusing drive of the current initial operation, inthe event that the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the secondelectrode 16 has been carried out as the fusing drive of the immediatelypreceding initial operation.

FIGS. 15A and 15B are graphs specifically illustrating an advantage ofsuperimposing the direct current in the fusing drive. FIG. 15A shows oneexample of a drive waveform, in the same way as FIG. 14, while FIG. 15Bshows the temperature of the leading extremity 15 a of the firstelectrode 15. In FIG. 15A, a horizontal axis shows the time, and avertical axis shows the current. In this case, the frequency of thedrive waveform is taken to be 100 Hz, and a direct current of a size 10%of the original rectangular wave is superimposed on the side on whichthe first electrode 15 becomes the anode. Also, the average power is 170W. In FIG. 15B, a horizontal axis shows the time, and a vertical axisshows the temperature. Also, a solid line in the graph indicates thesimulated temperature of the protruding leading extremity 15 a, a dottedline indicates the one cycle average temperature of the leadingextremity 15 a, and a chain line indicates the average temperature inthe anode period of the leading extremity 15 a. A graph with nosuperposition of the direct current, as a comparison example vis-à-visFIGS. 15A and 15B, is the same as the drive waveform and the like of therated drive in the steady operation shown in FIGS. 12A and 12B.

As is clear when comparing FIG. 15B and FIG. 12B, it can be understoodthat, compared with the case of there being no superposition of thedirect current, in the case of superimposing the 10% direct current onthe first electrode 15 side, as the temperature at the leading extremity15 a anode time (the peak value and the average value), and the onecycle average temperature and anode period average temperature of theleading extremity 15 a rise, and as the temperature of the leadingextremity 15 a in the anode period rises overall in the latter half,there is more likelihood of increasing the volumes of the leadingextremity 15 a, and the fused portions 62 and 64 in the peripherythereof.

FIFTH OPERATIONAL EXAMPLE

Hereafter, a description will be given of a fifth operational examplewith the fusing drive. FIG. 16A is a graph conceptually illustrating theinitial operation of the arc tube 1, in the operational example. In thegraph, a horizontal axis shows the time, and a vertical axis shows thecurrent. In the case of the fifth operational example, during thelaunching period of the fusing drive, a superimposed wave, in which agradually increasing triangular wave is superimposed on the rectangularwave, being supplied, although an average current value thereof ismaintained at D0, a peal value of the superimposed wave is D1. Herein,taking a ratio of the peak value D1 with respect to the average currentvalue D0 as the triangular wave jump rate of the superimposed wave, thetriangular wave jump rate D1/D0 increases more than a triangular wavejump rate 1 of the rectangular wave. By adjusting the triangular wavejump rate, it is possible to increase the temperatures of the twoelectrodes 15 and 16 by a desired amount in the latter halves of theanode periods of the first and second electrodes 15 and 16. With thiskind of superimposed waveform, it being possible to make the cumulativeenergy supplied in the latter half of the anode period of each of thefirst electrode 15 and the second electrode 16 at the time of the fusingdrive greater than the cumulative energy supplied in the latter half ofthe anode period of the corresponding electrode at the time of the rateddrive, it is possible to reliably increase the volumes of the fusedportions 62 and 64 of the leading extremity sides of the first electrode15 and the second electrode 16 in comparison with the time of the rateddrive during the steady operation. In FIG. 16B, the currentcharacteristic L52 of the dotted line indicates a superimposed wave typedrive waveform corresponding to the low level fusing drive for theelectrode which has become a little difficult to fuse when the aging ofthe arc tube 1 has progressed to a certain extent, and the currentcharacteristic L53 of the chain line indicates a superimposed wave typedrive waveform corresponding to the low level fusing drive for theelectrode which has become considerably difficult to fuse when the agingof the arc tube 1 has further progressed.

The description given heretofore has been one in which the volumes ofthe fused portions 62 and 64 are increased for both the first and secondelectrodes 15 and 16, but it is possible to increase the volumes of thefused portions 62 and 64 for only either one of the first electrode 15or the second electrode 16. In this case, the triangular wave jump rateof the superimposed wave of only either one of the first electrode 15 orthe second electrode 16 is increased when it becomes the anode.Furthermore, in the event of alternately increasing the triangular wavejump rate for the first and second electrodes 15 and 16 during thelaunching period, by a unit of each initial operation, it is possible toalternately heat the leading extremity sides of the two electrodes 15and 16 in a balanced manner. Alternatively, in the case of carrying outthe fusing drive for only either one of the first electrode 15 or thesecond electrode 16, by the unit of each initial operation, the firstelectrode 15 and the second electrode 16 are alternately made the mainfusion subject by carrying out the fusing drive increasing the volumesof the fused portions 62 and 64 of the leading extremity sides of thesecond electrode 16 as the fusing drive of the current initialoperation, in the event that the fusing drive increasing the volumes ofthe fused portions 62 and 64 of the leading extremity sides of the firstelectrode 15 has been carried out in the immediately preceding initialoperation, and carrying out the fusing drive increasing the volumes ofthe fused portions 62 and 64 of the leading extremity sides of the firstelectrode 15 as the fusing drive of the current initial operation, inthe event that the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the secondelectrode 16 has been carried out as the fusing drive of the immediatelypreceding initial operation.

FIGS. 17A and 17B are graphs specifically illustrating an advantage ofsuperimposing the triangular wave in the fusing drive. FIG. 17A showsone example of a drive waveform, in the same way as FIG. 16A, while FIG.17B shows the temperature of the leading extremity 15 a of the firstelectrode 15. In FIG. 17A, a horizontal axis shows the time, and avertical axis shows the current value. In this case, the frequency ofthe drive waveform is taken to be 100 Hz, and the triangular wave jumprate of the superimposed wave is taken to be 20%. Also, the averagepower is 170 W. In FIG. 17B, a horizontal axis shows the time, and avertical axis shows the temperature. Also, a solid line in the graphindicates the simulated temperature of the protruding leading extremity15 a, a dotted line indicates the one cycle average temperature of theleading extremity 15 a, and a chain line indicates the averagetemperature in the anode period of the leading extremity 15 a.

Meanwhile, FIG. 18A, being a graph for a comparison, shows one exampleof a drive waveform of the rated drive in the steady operation, whileFIG. 18B shows the temperature of the leading extremity 11 a of thefirst electrode 15 in a case of using the drive waveform of FIG. 18A. Inthis case, as can be understood from FIG. 18A, the triangular wave jumprate of the superimposed wave is taken to be 10%. Also, in FIG. 18B, inthe same way as in FIG. 17B, a solid line in the graph indicates thesimulated temperature of the protruding leading extremity 15 a, a dottedline indicates the one cycle average temperature of the leadingextremity 15 a, and a chain line indicates the average temperature inthe anode period of the leading extremity 15 a. As is clear whencomparing FIG. 18B and FIG. 17B, it can be understood that, comparedwith the case of making the triangular wave jump rate 10%, in the caseof making the triangular wave jump rate 20%, as the temperature at theleading extremity 15 a anode time (the peak value and the average value)and the one cycle average temperature of the leading extremity 15 arise, and as the temperatures of the leading extremities 15 a and 16 ain the anode periods rise farther in the latter half, there is morelikelihood of increasing the volumes of the leading extremities 15 a and16 a, and the fused portions 62 and 64 on the peripheries thereof.

In the fifth operational example, a peak position of the superimposedwave is arranged to be at an end of the anode period by superimposingthe gradually increasing triangular wave on the rectangular wave, but itis also possible to arrange for the peak position to come at an optionaltime during the anode period. For example, it is also acceptable toarrange in such a way that, superimposing the gradually increasingtriangular wave on the rectangular wave, the peak position comes at abeginning of the anode period. In this case, the cumulative energysupplied in the former half of the anode period of each of the firstelectrode 15 and the second electrode 16 is greater at the time of thefusing drive than at the time of the rated drive. Generally, by makingthe cumulative energy supplied to the electrode in at least one portionof the anode period greater than at the time of the rated drive, it ispossible to increase the temperatures of the electrodes 15 and 16 by adesired amount. For this reason, it is possible to reliably increase thevolumes of the fused portions 62 and 64 of the leading extremity sidesof the first electrode 15 and the second electrode 16 in comparison withthe time of the rated drive during the steady operation. However, from apoint of being able to increase the temperatures of the electrodes 15and 16 when switching from the anode to the cathode, and being able tostabilize the position of the arc, it is preferable to arrange that thepeak position of the superimposed wave comes at the end of the anodeperiod.

SIXTH OPERATIONAL EXAMPLE

Hereafter, a description will be given of a sixth operational examplewith the fusing drive. FIG. 19A shows the initial operation of the arctube 1 in the operational example, while FIG. 19B shows the temperatureof the leading extremity 15 a of the first electrode 15. In FIG. 19A, ahorizontal axis shows the time, and a vertical axis shows the currentvalue. In this case, the frequency of the drive waveform is taken to be100 Hz, and the drive waveform is such that a pulse wave is superimposedon an end portion of former and latter half cycles of the rectangularwave, the pulse wave having a height 40% of the former half. Also, theaverage power is 170 W. Meanwhile, in FIG. 19B, a horizontal axis showsthe time, and a vertical axis shows the temperature. Also, a solid linein the graph indicates the simulated temperature of the protrudingleading extremity 15 a, a dotted line indicates the one cycle averagetemperature of the leading extremity 15 a, and a chain line indicatesthe average temperature in the anode period of the leading extremity 15a.

Meanwhile, FIG. 20A, being a graph for a comparison, shows one exampleof a drive waveform of the rated drive in the steady operation, whileFIG. 20B shows the temperature of the leading extremity 15 a of thefirst electrode 15 in a case of using the drive waveform of FIG. 20A. Inthis case, as can be understood from FIG. 20A, the drive waveform issuch that a pulse wave is superimposed on the end portion of the formerand latter half cycles of the rectangular wave, the pulse wave having aheight 20% of the former half. Also, in FIG. 20B, in the same way as inFIG. 19B, a solid line in the graph indicates the simulated temperatureof the protruding leading extremity 15 a, a dotted line indicates theone cycle average temperature of the leading extremity 15 a, and a chainline indicates the average temperature in the anode period of theleading extremity 15 a. As is clear when comparing FIG. 20B and FIG.19B, it can be understood that, compared with the case of superimposingthe 20% projection, in the case of superimposing the 40% projection, asthe peak values of the temperatures of the leading extremities 15 a and16 a in the anode periods rise, there is more likelihood of increasingthe volumes of the leading extremities 15 a and 16 a, and the fusedportions 62 and 64 on the peripheries thereof. That is, with the drivewaveform wherein a pulse wave is superimposed at the end of therectangular wave, it is possible to make the cumulative energy suppliedin the latter half of the anode period of each of the first electrode 15and the second electrode 16 at the time of the fusing drive greater thanthe cumulative energy supplied in the latter half of the anode period ofthe corresponding electrode at the time of the rated drive, andfurthermore, it is possible to make the maximum value of the currentsupplied in the anode period of each of the first electrode 15 and thesecond electrode 16 at the time of the fusing drive greater than themaximum value of the current supplied in the anode period of the firstelectrode 15 at the time of the rated drive during the steady operation.By this means, there is more likelihood of increasing the volumes of thefused portions 62 and 64 at the time of the fusing drive, compared withthe time of the rated drive.

The description given heretofore has been one in which the volumes ofthe fused portions 62 and 64 are increased for both the first and secondelectrodes 15 and 16, but it is possible to increase the volumes of thefused portions 62 and 64 for only either one of the first electrode 15or the second electrode 16. In this case, the projection is superimposedon the rectangular wave only when either one of the first electrode 15or the second electrode 16 becomes the anode. In this way, in the caseof carrying out the fusing drive for only either one of the firstelectrode 15 or the second electrode 16, the first electrode 15 and thesecond electrode 16 are alternately made the main fusion subject bycarrying out the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the secondelectrode 16 as the fusing drive of the current initial operation, inthe event that the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the first electrode15 has been carried out in the immediately preceding initial operation,and carrying out the fusing drive increasing the volumes of the fusedportions 62 and 64 of the leading extremity sides of the first electrode15 as the fusing drive of the current initial operation, in the eventthat the fusing drive increasing the volumes of the fused portions 62and 64 of the leading extremity sides of the second electrode 16 hasbeen carried out as the fusing drive of the immediately precedinginitial operation.

Also, with the low level fusing drive for the electrode when the agingof the arc tube 1 has progressed to a certain extent, it is possible tosecure the volumes of the leading extremities 15 a and 16 a, and thefused portions 62 and 64 on the peripheries thereof, by furtherincreasing a height and width of the pulse wave superimposed on the endportion of the former and latter half cycles of the rectangular wave.

SEVENTH OPERATIONAL EXAMPLE

Hereafter, a description will be given of a seventh operational examplewith the fusing drive. FIG. 21A shows the initial operation of the arctube 1, in the operational example, while FIG. 21B shows the temperatureof the leading extremity 15 a of the first electrode 15. In FIG. 21A, ahorizontal axis shows the time, and a vertical axis shows the currentvalue. In this case, the frequency of the drive waveform is taken to be80 Hz, and the average power is 170 W. Meanwhile, in FIG. 21B, ahorizontal axis shows the time, and a vertical axis shows thetemperature. Also, a solid line in the graph indicates the simulatedtemperature of the protruding leading extremity 15 a, a dotted lineindicates the one cycle average temperature of the leading extremity 15a, and a chain line indicates the average temperature in the anodeperiod of the leading extremity 15 a. A graph with a frequency of 100Hz, as a comparison example vis-à-vis FIGS. 21A and 21B, is the same asthe drive waveform and the like of the rated drive in the steadyoperation shown in FIGS. 12A and 12B.

As is clear when comparing FIG. 21B and FIG. 12B, it can be understoodthat, in the case of making the frequency lower, as the maximumtemperature of the leading extremity 15 a in the anode period and theaverage temperature of the leading extremity 15 a in the anode periodrise, and the temperatures of the leading extremities 15 a and 16 a inthe anode period rise overall in the latter half; there is morelikelihood of increasing the volumes of the leading extremities 15 a and16 a, and the fused portions 62 and 64 on the peripheries thereof. Thatis, with the drive waveform wherein the frequency of the rectangularwave and the like is reduced, as well as it being possible to make thecumulative energy supplied in the anode period of each of the firstelectrode 15 and the second electrode 16 at the time of the fusing drivegreater than the cumulative energy supplied in the latter half of theanode period of the corresponding electrode at the time of the rateddrive, it is possible to make the cumulative energy supplied in thelatter half of the anode period of each of the first electrode 15 andthe second electrode 16 at the time of the fusing drive greater than thecumulative energy supplied in the latter half of the anode period of thecorresponding electrode at the time of the rated drive. By this means,there is more likelihood of increasing the volumes of the fused portions62 and 64 at the time of the fusing drive, compared with the time of therated drive.

Also, with the low level fusing drive for the electrode when the agingof the arc tube 1 has progressed to a certain extent, it is possible tosecure the volumes of the leading extremities 15 a and 16 a, and thefused portions 62 and 64 on the peripheries thereof, by further reducingthe frequency.

SPECIFIC CONTROL EXAMPLE

FIGS. 22 and 23 are flowcharts illustrating operations of the lightsource drive device 70. Firstly, after turning on a power and before thestart of the lighting, the evaluating portion 75 retrieves operationalinformation of an immediately preceding lighting time of the lightsource unit 10 from the data storage portion 76, and determines whetheror not, in the immediately preceding lighting of the light source unit10, a reproduction drive corresponding to the kind of special operationillustrated in FIG. 5B and FIG. 5C has been in progress at a point ofswitching from the steady operation to a turning off operation (stepS11).

If it is determined in step S11 that, in the immediately precedinglighting of the light source unit 10, a reproduction drive has been inprogress at the point of switching from the steady operation to theturning off operation, a regular initial drive power supply condition,among power supply conditions of the initial operation, is retrievedfrom a drive control table stored in the data storage portion 76, and areproduction drive power supply condition, among power supply conditionsof the steady operation, is retrieved (step S12). In the event that thereproduction drive has been interrupted in the immediately precedinglighting, it is arranged in such a way that the reproduction of theextremity is restarted, and an appropriate restorative operation isexecuted, without executing again from the fusing drive.

Next, the controller 70 b, controlling the lighting device 70 a based onthe regular initial drive power supply condition of the initialoperation retrieved in step S12, controls the regular initial drive ofthe initial operation, including the launching operation, from thestarting of the arc tube 1 (step S13).

Next, the controller 70 b, controlling the lighting device 70 a based onthe reproduction drive power supply condition of the steady operationretrieved in step S12, controls the reproduction drive of the steadyoperation of the arc tube 1 (step S14).

Herein, the evaluating portion 75 determines whether or not, during thesteady operation, an interrupting request signal requesting a finish ofthe light source unit 10 lighting operation has been input (step S15).If there has been an input of this kind of interrupting request signal,a process is interrupted even when the reproduction drive is inprogress, the fact that the reproduction drive has been in progress atthe point of switching from the steady operation to the turning offoperation is recorded in the data storage portion 76, and a shift ismade to the turning off operation.

If it is determined, in step S15, that there has been no input of aninterrupting request signal requesting the finish of the light sourceunit 10 lighting operation, the evaluating portion 75 determines whetheror not the reproduction drive is completed (step S16). If thereproduction drive is not completed, that is, in the event that thereproduction drive is in progress, the controller 70 b returns to stepS14, and continues the reproduction drive. The reproduction drive beingexecuted at an outset of the steady operation, in the event that a largeleading extremity 15 a or 16 a has grown at the leading extremity sideof the subject electrode, of the two electrodes 15 and 16, it isdetermined that the reproduction drive is completed.

If it is determined, in step S16, that the reproduction drive iscompleted, the controller 70 b records the fact that the reproductiondrive is completed in the data storage portion 76, and retrieves aregular steady drive power supply condition of the steady operation fromthe drive control table stored in the data storage portion 76 (stepS31). Specifically, a setting value of a current value, a frequency, atriangular wave jump rate, a duty ratio and the like, for the regularsteady drive at the time of the steady operation, are retrieved.

If it is determined in step S11 that, in the immediately precedinglighting of the light source unit 10, no reproduction drive has been inprogress at the point of switching from the steady operation to theturning off operation, the evaluating portion 75 retrieves theoperational information of the immediately preceding lighting time ofthe light source unit 10 from the data storage portion 76, anddetermines whether or not a special operation should be executed in theinitial operation of the arc tube 1 (step S21).

Specifically, in the event that the cumulative lit time has exceeded apredetermined value at an immediately preceding lighting finishing pointand, as illustrated in FIG. 5A, the aging of the arc tube 1 hasprogressed and reached a condition calling for restoration, wherein acomplete restoration of the electrode leading extremity is needed, it isdetermined that the high level fusing drive should be executed in theinitial operation. In this step S21, it is also possible to determinewhether a fusing drive for a repair or for a restoration should beexecuted, depending on whether or not a voltage supplied to the arc tube1 at the time of the steady operation before the immediately precedinglighting finish is as high as, or higher than, a voltage indicating thekind of condition calling for restoration, as illustrated in FIG. 5A,wherein the aging of the arc tube 1 has progressed and the completerestoration of the electrode leading extremity is needed.

Next, the evaluating portion 75, as an associated process of step S21,determines which of the first electrode 15 and the second electrode 16to carry out the fusing drive for. Specifically, when the high levelfusing drive corresponding to the immediately preceding specialoperation has been executed, in the event that a first high level fusingdrive, which fuses the leading extremity side (the leading extremity 15a etc.) of the first electrode 15 more than the leading extremity side(the leading extremity 16 a etc.) of the second electrode 16, has beenexecuted, the evaluating portion 75, as well as determining that asecond high level fusing drive, which fuses the leading extremity side(the leading extremity 16 a etc.) of the second electrode 16 more thanthe leading extremity side (the leading extremity 15 a etc.) of thefirst electrode 15, should be executed as the high level fusing drive onthe current occasion, stores this information in the data storageportion 76. That is, the evaluating portion 75, when carrying out thehigh level fusing drive corresponding to the special operation,determines which, of the first high level fusing drive and the secondhigh level fusing drive, to execute as the high level fusing drivecorresponding to the special operation on the current occasion, in orderthat the first high level fusing drive and the second high level fusingdrive are carried out alternately.

Next, the evaluating portion 75, as an associated process of step S21,determines on whose leading extremity side, the first electrode 15 orthe second electrode 16, to carry out the reproduction drive of thespecial operation. Specifically, in the event that it is determined thatthe first high level fusing drive, which forms the fused portion 62(refer to FIG. 5B) on the first electrode 15 side in the high levelfusing drive of the special operation, is to be executed, the evaluatingportion 75 determines that a first reproduction drive, which reproducesthe leading extremity 15 a of the first electrode 15 in the steady driveof the special operation, should be executed, while in the event that itis determined that the second high level fusing drive, which forms thefused portion 62 (refer to FIG. 5B) on the second electrode 16 side inthe fusing drive, is to be executed, the evaluating portion 75determines that a second reproduction drive, which reproduces theleading extremity 16 a of the second electrode 16 in the steady drive ofthe special operation, should be executed.

If it is determined, in step S21, that the high level fusing drive ofthe special operation should be executed as the initial operation of theare tube 1, the controller 70 b, in accordance with the evaluationresult of step S21, retrieves a special operation high level fusingdrive power supply condition, among the power supply conditions of theinitial operation and, in accordance with the evaluation result of stepS21, retrieves a special operation reproduction drive power supplycondition, among the power supply conditions of the steady operation,from the drive control table stored in the data storage portion 76 (stepS22). Specifically, a setting value of a current value, a frequency, aduty ratio and the like, for the high level fusing drive are retrieved,and the setting value of the current value, the frequency, thetriangular wave jump rate, the duty ratio and the like, for thereproduction drive are retrieved.

Next, the controller 70 b, controlling the lighting device 70 a based onthe high level fusing drive power supply condition of the initialoperation retrieved in step S22, controls the high level fusing drive ofthe initial operation, including the launching operation, from thestarting of the arc tube 1 (step S23).

Next, the controller 70 b, controlling the lighting device 70 a based onthe reproduction drive power supply condition of the steady operationretrieved in step S22, controls the reproduction drive of the steadyoperation of the arc tube 1 (step S24).

Herein, the evaluating portion 75 determines whether or not, during thesteady operation, an interrupting request signal requesting the finishof the light source unit 10 lighting operation has been input (stepS25). If there has been an input of this kind of interrupting requestsignal, the process is interrupted even when the reproduction drive isin progress, the fact that the reproduction drive has been in progressat the point of switching from the steady operation to the turning offoperation is recorded in the data storage portion 76, and a shift ismade to the turning off operation.

If it is determined, in step S25, that there has been no input of aninterrupting request signal requesting the finish of the light sourceunit 10 lighting operation, the evaluating portion 75 determines whetheror not the reproduction drive is completed (step S26). If thereproduction drive is not completed, that is, in the event that thereproduction drive is in progress, the controller 70 b returns to stepS24, and continues the reproduction drive. The reproduction drive beingexecuted at the outset of the steady operation, in the event that alarge leading extremity 15 a or 16 a has grown at the leading extremityside of the subject electrode, of the two electrodes 15 and 16, it isdetermined that the reproduction drive is completed.

If it is determined, in step S26, that the reproduction drive iscompleted, the controller 70 b records the fact that the reproductiondrive is completed in the data storage portion 76, and retrieves theregular steady drive power supply condition of the steady operation fromthe drive control table stored in the data storage portion 76 (stepS31). Specifically, the setting value of the current value, thefrequency, the triangular wave jump rate, the duty ratio and the like,for the regular steady drive at the time of the steady operation, areretrieved.

Next, the controller 70 b, based on the regular steady drive powersupply condition of the steady operation retrieved in step S31, controlsthe operating condition of the lighting device 70 a, that is, theregular steady drive of the steady operation of the arc tube 1 (stepS32).

Herein, the evaluating portion 75 determines whether or not, during thesteady operation, an interrupting request signal requesting the finishof the light source unit 10 lighting operation has been input (step 33).If there has been an input of this kind of interrupting request signal,information indicating a current condition of the arc tube 1, such as acurrent cumulative lit time, and a voltage currently being supplied tothe arc tube 1, is recorded in the data storage portion 76, and a shiftis made to the turning off operation.

If it is determined, in step S21, that the special operation should notbe executed in the initial operation of the arc tube 1, the evaluatingportion 75 retrieves the operational information of the immediatelypreceding lighting time of the light source unit 10 from the datastorage portion 76, and determines whether or not the low level fusingoperation should be executed in the initial operation of the arc tube 1(step S41).

Specifically, in the event that it is determined that, at theimmediately preceding lighting finishing point, as illustrated in FIG.4A, the aging of the arc tube 1 has progressed, the concavities andconvexities 61 and 63 have occurred, and it will be difficult as thingsstand to maintain the shape of the leading extremity 15 a and theleading extremity side area 15 g of the first electrode 15, it isdetermined that the low level fusing drive should be executed in theinitial operation. In this step S41, it is also possible to determinewhether or not the low level fusing drive should be executed dependingon whether or not the voltage supplied to the arc tube 1 at the time ofthe steady operation before the immediately preceding lighting finish isas high as, or higher than, a voltage indicating the kind of conditionillustrated in FIG. 4A, wherein the aging of the arc tube 1 hasprogressed, and a maintenance of the electrode leading extremity shapeis needed. In the event that the aging of the arc tube 1 has progressed,and the leading extremities 15 a and 16 a of the first electrode 15 andthe second electrode 16 have become difficult to fuse, it is alsopossible to arrange in such a way as to determine that a drive waveformwhich increases the temperature of the leading extremities 15 a and 16 aof each of the electrodes 15 and 16 (such as the current characteristicsL12 and L13 of FIG. 6, the current characteristics L22 and L23 of FIG.8, the current characteristics L31 and L33 of FIG. 10, the currentcharacteristics L41 and L43 of FIG. 14, or the drive waveform of FIG.16B) should be executed. By this means, it is possible to secure thevolumes of the leading extremities 15 a and 16 a, and the fused portions62 and 64 on the peripheries thereof.

Next, the evaluating portion 75, as an associated process of step S41,determines which of the first electrode 15 and the second electrode 16to carry out the fusing drive for. Specifically, when the low levelfusing drive has been executed the immediately preceding time, in theevent that a first low level fusing drive, which fuses the leadingextremity side (the leading extremity 15 a etc.) of the first electrode15 more than the leading extremity side (the leading extremity 16 aetc.) of the second electrode 16, has been executed, the evaluatingportion 75, as well as determining that a second low level fusing drive,which fuses the leading extremity side (the leading extremity 16 a etc.)of the second electrode 16 more than the leading extremity side (theleading extremity 15 a etc.) of the first electrode 15, should beexecuted as the low level fusing drive on the current occasion, storesthis information in the data storage portion 76. That is, the evaluatingportion 75, when carrying out the low level fusing drive, determineswhich, of the first low level fusing drive and the second low levelfusing drive, to execute as the low level fusing drive corresponding tothe current occasion, in order that the first low level fusing drive andthe second low level fusing drive are carried out alternately.

If it is determined, in step S41, that the low level fusing drive shouldbe executed as the initial operation of the arc tube 1, the controller70 b, in accordance with the evaluation result of step S41, retrieves alow level fusing drive power supply condition, among the power supplyconditions of the initial operation, from the drive control table storedin the data storage portion 76 (step S42). Specifically, a setting valueof a current value, a frequency, a duty ratio and the like, for the lowlevel fusing drive are retrieved, and the setting value of the currentvalue, the frequency, the triangular wave jump rate, the duty ratio andthe like, for the regular steady drive are retrieved.

Next, the controller 70 b, controlling the lighting device 70 a based onthe low level fusing drive power supply condition of the initialoperation retrieved in step S42, controls the low level fusing drive ofthe initial operation, including the launching operation, from thestarting of the arc tube 1 (step S43).

If it is determined, in step S21, that the special operation should notbe executed in the initial operation of the arc tube 1, and furthermore,if it is determined, in step S41, that the low level fusing drive shouldnot be executed in the initial operation of the arc tube 1, theevaluating portion 75 retrieves a regular initial drive power supplycondition, among the power supply conditions of the initial operation,and retrieves a regular steady drive power supply condition, among thepower supply conditions of the steady operation, from the drive controltable stored in the data storage portion 76 (step S44). Specifically, asetting value of a current value, a frequency, a duty ratio and thelike, for the regular initial drive are retrieved, and a setting valueof a current value, a frequency, a triangular wave jump rate, a dutyratio and the like, for the regular steady drive are retrieved.

Next, the controller 70 b, controlling the lighting device 70 a based onthe regular initial drive power supply condition of the initialoperation retrieved in step S44, controls the regular initial drive ofthe initial operation, including the launching operation, from thestarting of the arc tube 1 (step S45).

Next, after carrying out the low level fusing drive in step S43 or theregular initial drive in step S45, the controller 70 b, controlling thelighting device 70 a based on the regular steady drive power supplycondition of the steady operation retrieved in step S42 or step S44,controls the regular steady drive of the steady operation of the arctube 1 (step S46).

Herein, the evaluating portion 75 determines whether or not, during thesteady operation, an interrupting request signal requesting the finishof the light source unit 10 lighting operation has been input (stepS47). If it is determined that there has been no input of aninterrupting request signal requesting the finish of the light sourceunit 10 lighting operation, the controller 70 b returns to step S46, andcontinues the regular steady drive.

If there has been an input of an interrupting request signal in stepS47, the information indicating the current condition of the arc tube 1,such as the current cumulative lit time, and the voltage currently beingsupplied to the arc tube 1, is recorded in the data storage portion 76,and a shift is made to the turning off operation.

As is clear from the above description, with the light source apparatus100 of the embodiment, the controller 70 b being able to operate withthe fusing drive, with the fusing drive, at any timing during theinitial operation, it makes the volumes of the fused portions 62 and 64of the first electrode 15 or the second electrode 16 larger than thevolumes of the fused portions of the leading edge side of the firstelectrode 15 or the second electrode 16 at the time of the rated driveduring the steady operation. Therefore, the repair or the restoration ofthe electrodes 15 and 16 utilizing the lighting start period beingpossible, it is possible to suppress the occurrence of the flicker andthe arc jump. Also, by maintaining the electrode leading extremity in agood shape, and keeping the illuminance of the light source apparatushigh, it is possible to achieve a lengthening of a life span. Accordingto the above, by increasing the fusion volume of the first electrode 15or the second electrode 16 without interrupting the steady operation, itis possible to prevent a brightness of a source light or projectionimage from fluctuating after an actual start of use.

Projector

FIG. 24 is a conceptual diagram for illustrating a structure of aprojector in which is embedded the light source apparatus 100 of FIG. 1.A projector 200 includes the light source apparatus 100, an illuminationoptical system 20, a color separating optical system 30, a lightmodulator 40, a cross dichroic prism 50, and a projection lens 60.Herein, the light modulator 40 includes three liquid crystal lightvalves 40 a, 40 b and 40 c, which have identical structures.

In the heretofore described projector 200, the light source apparatus100, including the light source unit 10 and the light source drivedevice 70 shown in FIG. 1, emits an illumination light for illuminatingthe light modulator 40, that is, the liquid crystal light valves 40 a,40 b and 40 c, via the illumination optical system 20, and the like.

The illumination optical system 20 including a parallelizing lens 22,which parallelizes a light flux direction of a source light, first andsecond fly-eye lenses 23 a and 23 b, which configure an integratedoptical system for dividing and superimposing light, a polarizationconversion element 24, which aligns a polarization direction of thelight, a superposition lens 25, which superimposes light which haspassed through the two fly-eye lenses 23 a and 23 b, and a mirror 26,which bends an optical path of the light, a homogenized illuminationlight of an approximately white color is formed thereby. In theillumination optical system 20, the parallelizing lens 22 converts aflux direction of an illumination light projected from the light sourceunit 10 so as to be approximately parallel. The first and second fly-eyelenses 23 a and 23 b being configured of a plurality of element lenseseach of which is disposed in a matrix form, the light which has passedthrough the parallelizing lens 22 is divided and individually gatheredby the element lenses which configure the first fly-eye lens 23 a, whiledivided light fluxes from the first fly-eye lens 23 a are projected atan appropriate angle of divergence by the element lenses which configurethe second fly-eye lens 23 b. The polarization conversion element 24,being formed of an array which makes a PBS, a mirror, a retarder, andthe like, a single group of elements, has a function of arranging apolarization direction of each partial light flux divided by the firstfly-eye lens 23 a into a unidirectional linear polarization. Thesuperposition lens 25 appropriately gathers, as a whole, illuminationlight which has passed through the polarization conversion element 24,enabling a superimposed illumination of an illumination area of theliquid crystal light valves 40 a, 40 b and 40 c, which are variouslycolored light modulating devices of a latter stage.

The color separating optical system 30 including first and seconddichroic mirrors 31 a and 31 b, reflecting mirrors 32 a, 32 b and 32 c,and three field lenses 33 a, 33 b and 33 c, as well as separating theillumination light homogenized by the illumination optical system 20into three colors red (R), green (G) and blue (B), leads each coloredlight to the liquid crystal light valves 40 a, 40 b and 40 c of thelatter stage. To describe in more detail, firstly, the first dichroicmirror 31 a transmits the R light, of the three colors RGB, and reflectsthe G light and the B light. Also, the second dichroic mirror 31 breflects the G light, of the two colors GB, and transmits the B light.Next, in the color separating optical system 30, the R light transmittedthrough the first dichroic mirror 31 a falls incident, via thereflecting mirror 32 a, on the field lens 33 a, for adjusting an angleof incidence. Also, the G light, which is reflected by the firstdichroic mirror 31 a, and furthermore, is also reflected by the seconddichroic mirror 31 b, falls incident on the field lens 33 b, foradjusting an angle of incidence. Furthermore, the B light which haspassed through the second dichroic mirror 31 b falls incident, via relaylenses LL1 and LL2, and the reflecting mirrors 32 b and 32 c, on thefield lens 33 c, for adjusting an angle of incidence.

Each liquid crystal light valve 40 a, 40 b and 40 c configuring thelight modulator 40 is a non-light emitting type of light modulatingdevice which modulates a spatial intensity distribution of incidentillumination light. The liquid crystal light valves 40 a, 40 b and 40 cinclude three liquid crystal panels 41 a, 41 b and 41 c, each of whichis illuminated corresponding to each colored light projected from thecolor separating optical system 30, three first polarization filters 42a, 42 b and 42 c, which are respectively disposed on an incidence sideof each liquid crystal panel 41 a, 41 b and 41 c, and three secondpolarization filters 43 a, 43 b and 43 c, which are respectivelydisposed on a projection side of each liquid crystal panel 41 a, 41 band 41 c. The R light transmitted through the first dichroic mirror 31 afalls incident, via the field lens 33 a etc., on the liquid crystallight valve 40 a, and illuminates the liquid crystal panel 41 a of theliquid crystal light valve 40 a. The G light reflected by both the firstand second dichroic mirrors 31 a and 31 b falls incident, via the fieldlens 33 b etc., on the liquid crystal light valve 40 b, and illuminatesthe liquid crystal panel 41 b of the liquid crystal light valve 40 b.The B light, which is reflected by the first dichroic mirror 31 a andtransmitted through the second dichroic mirror 31 b, falls incident, viathe field lens 33 c etc., on the liquid crystal light valve 40 c, andilluminates the liquid crystal panel 41 c of the liquid crystal lightvalve 40 c. Each liquid crystal panel 41 a to 41 c modulating thespatial intensity distribution of the polarization direction of theincident illumination light, the three colors of light falling incidentrespectively on the liquid crystal panels 41 a to 41 c have apolarization condition adjusted in pixel units in accordance with adrive signal or an image signal input into the liquid crystal panels 41a to 41 c as an electrical signal. At this time, as well as thepolarization direction of the illumination light falling incident on theliquid crystal panels 41 a to 41 c being adjusted by the firstpolarization filters 42 a to 42 c, modulated light of a predeterminedpolarization direction is removed from modulated light projected fromthe liquid crystal panels 41 a to 41 c by the second polarizationfilters 43 a to 43 c. According to the above, each liquid crystal lightvalve 40 a, 40 b and 40 c respectively forms an image light of acorresponding color.

The cross dichroic prism 50 synthesizes the colored image lights fromthe liquid crystal light valves 40 a, 40 b and 40 c. To describe in moredetail the cross dichroic prism 50 forming an approximate square, in aplanar view, in which four orthogonal prisms are stuck together, a pairof dielectric multilayer films 51 a and 51 b intersecting in an X shapeare formed at an interface where the orthogonal prisms are stucktogether. One first dielectric multilayer film 51 a reflects the Rlight, while the other second dielectric multilayer film 51 b reflectsthe B light. The cross dichroic prism 50 reflects the R light from theliquid crystal light valve 40 a with the dielectric multilayer film 51a, projecting it on a travel direction right side, projects the G lightfrom the liquid crystal light valve 40 b straight ahead through thedielectric multilayer films 51 a and 51 b, and reflects the B light fromthe liquid crystal light valve 40 c with the dielectric multilayer film51 b, projecting it on a travel direction left side. By so doing, the Rlight, G light and B light are synthesized by the cross dichroic prism50, and a synthesized light, which is an image light consisting of colorimages, is formed.

The projection lens 60, being a projection optical system, enlarges theimage light, consisting of the synthesized light formed via the crossdichroic prism 50, by a desired enlargement rate, and projects a colorimage onto a screen (not shown).

The invention, not being limited to the heretofore described embodiment,can be embodied in various aspects without departing from the scopethereof with, for example, the following kinds of modification alsobeing possible.

For example, in the heretofore described embodiment, as a lamp used inthe light source unit 10, various kinds of article, such as a highpressure mercury lamp or a metal halide lamp, can be considered.

Also, in the projector 200 of the heretofore described embodiment, thepair of fly-eye lamps 23 a and 23 b are used to divide the light fromthe light source apparatus 100 into a plurality of partial luminousfluxes, but the invention can also be applied to a projector which doesnot use this kind of fly-eye lens, that is, a lens array. Furthermore,it is also possible to replace the fly-eye lenses 23 a and 23 b with arod integrator.

Also, in the heretofore described projector 200, the polarizationconversion element 24, which polarizes the light from the light sourceapparatus 100 in a specific direction, is used, but the invention canalso be applied to a projector which does not use this kind ofpolarization conversion element 24.

Also, in the heretofore described embodiment, a description has beengiven of an example of a case in which the invention is applied to atransmission type projector, but the invention can also be applied to areflection type projector. Herein, “transmission type” means that it isa type wherein a liquid crystal light valve, including a liquid crystalpanel and the like, transmits light, while “reflection type” means thatit is a type wherein a liquid crystal light valve reflects light. It isalso acceptable that a light modulating device, not being limited to aliquid crystal panel or the like, is a light modulating device using,for example, a micromirror.

Also, as a projector, there are a front screen projector, which carriesout an image projection from a direction in which a projection screen isviewed, and a back screen projector, which carries out an imageprojection from a side opposite to the direction in which the projectionscreen is viewed, but the configuration of the projector shown in FIG.24 can be applied to either.

Also, in the heretofore described embodiment, only the example of theprojector 200 using the three liquid crystal panels 41 a to 41 c isgiven, but the invention can also be applied to a projector using onlyone liquid crystal panel, a projector using two liquid crystal panels,or a projector using four or more liquid crystal panels.

Also, in the heretofore described embodiment, the modulation of eachcolored light is carried out using the color separating optical system30, the liquid crystal light valves 40 a, 40 b and 40 c, and the likebut, instead of this, it is also possible to carry out the modulationand synthesis of the colored lights by using, for example, a combinationof a color foil illuminated by the light source apparatus 100 and theillumination optical system 20, and a device, configured of pixels of amicromirror, irradiated with light transmitted through the color foil.

1. A light source apparatus comprising: an arc tube including a firstelectrode and a second electrode that carry out an emission of light dueto a discharge between them; and a drive unit that operates in at leasttwo operation modes, including: (i) a steady operation; and (ii) aninitial operation; during the steady operation mode, the drive unitsupplying a steady energy to the first electrode and the secondelectrode; and during the initial operation mode, the drive unitsupplying energy to the first electrode and the second electrode, thedrive unit operating differently during the initial operation mode thanduring the steady operation mode; the drive unit operating in theinitial operation mode before operating in the steady operation mode;the drive unit, in the initial operation mode, carrying out a fusingdrive making a volume of a fused portion of a leading extremity side ofat least one of the first electrode and the second electrode, greaterthan a volume of the fused portion of the leading extremity side of theat least one of the first electrode and the second electrode at a timeof a rated drive during the steady operation.
 2. The light sourceapparatus according to claim 1, the fusing drive of the initialoperation mode and the rated drive of the steady operation mode bothsupplying energy in an alternating current to the first electrode andthe second electrode, and at a time of the fusing drive in the initialoperation mode, by making a cumulative energy supplied to the at leastone of the first electrode and the second electrode in an anode periodof the at least one of the first electrode and the second electrodegreater than a cumulative energy supplied to the at least one of thefirst electrode and the second electrode in an anode period of the atleast one of the first electrode and the second electrode at the time ofthe rated drive during the steady operation mode, the volume of thefused portion being increased.
 3. The light source apparatus accordingto claim 1, the fusing drive of the initial operation mode and the rateddrive of the steady operation mode both supplying energy in analternating current to the first electrode and the second electrode, andat a time of the fusing drive in the initial operation, by making acumulative energy supplied to the at least one of the first electrodeand the second electrode in a latter half of an anode period of the atleast one of the first electrode and the second electrode greater than acumulative energy supplied to the at least one electrode in a latterhalf of an anode period of the at least one electrode at the time of therated drive during the steady operation mode, the volume of the fusedportion being increased.
 4. The light source apparatus according toclaim 1, the fusing drive of the initial operation mode and the rateddrive of the steady mode operation both supplying energy in analternating current to the first electrode and the second electrode, andat a time of the fusing drive in the initial operation mode, by making amaximum value of a current supplied in an anode period of the at leastone of the first electrode and the second electrode greater than amaximum value of a current supplied in an anode period of the at leastone of the first electrode and the second electrode at the time of therated drive during the steady operation mode, the volume of the fusedportion being increased.
 5. The light source apparatus according toclaim 1, the drive unit, in a launching operation period including atleast a period immediately before switching to the steady operationmode, during the time of the fusing drive of the initial operation,increasing a value of a current supplied to the at least one of thefirst electrode and the second electrode as time elapses.
 6. The lightsource apparatus according to claim 5, further comprising: an evaluatingportion that determines a degree of erosion of the arc tube, the driveunit, at the time of the fusing drive of the initial operation mode,increasing a rate of increase of the value of the current supplied tothe at least one of the first electrode and the second electrode duringthe launching operation period, in accordance with the degree of erosiondetermined by the evaluating portion.
 7. The light source apparatusaccording to claim 1, the drive unit, at the time of the fusing drive ofthe initial operation mode, increasing a value of a current supplied tothe at least one of the first electrode and the second electrode at anend of a launching operation provided after a start of the initialoperation.
 8. The light source apparatus according to claim 7, the driveunit, at the time of the fusing drive of the initial operation mode, inthe event that a voltage between the first electrode and the secondelectrode reaches a predetermined voltage value, temporarily increasingthe value of the current supplied to the at least one of the firstelectrode and the second electrode compared with that before reachingthe predetermined voltage value.
 9. The light source apparatus accordingto claim 7, further comprising: an evaluating portion that determines adegree of erosion of the arc tube, the drive unit, at the time of thefusing drive of the initial operation mode, increases the value of thecurrent supplied to the at least one of the first electrode and thesecond electrode at the end of the launching operation period, inaccordance with the degree of erosion determined by the evaluatingportion.
 10. The light source apparatus according to claim 2, the driveunit, at the time of the fusing drive of the initial operation mode,making an anode duty ratio relating to a current to one electrode, ofthe first electrode and second electrode, greater than at the time ofthe rated drive at the time of the steady operation mode.
 11. The lightsource apparatus according to claim 10, further comprising: anevaluating portion that determines a degree of erosion of the arc tube,the drive unit, at the time of the fusing drive of the initial operationmode, increasing the anode duty ratio relating to the one electrode inaccordance with the degree of erosion determined by the evaluatingportion.
 12. The light source apparatus according to claim 2, the driveunit, at the time of the fusing drive of the initial operation mode,superimposes a direct current, of a polarity the same as an anode of theone electrode, on the alternating current supplied to the firstelectrode and the second electrode.
 13. The light source apparatusaccording to claim 12, further comprising: an evaluating portion thatdetermines a condition of the arc tube, the drive unit, at the time ofthe fusing drive of the initial operation mode, increasing the directcurrent to be superimposed on the alternating current supplied to thefirst electrode and the second electrode in accordance with a degree oferosion determined by the evaluating portion.
 14. The light sourceapparatus according to claim 3, the drive unit, at the time of thefusing drive of the initial operation mode, making a current waveformsupplied to the at least one of the first electrode and the secondelectrode a superimposed wave, a triangular waveform being superimposedon a rectangular wave and a current gradually increasing over a halfcycle, a proportion of a maximum current value of the current waveform,with respect to an average current value in the anode period of the atleast one electrode, at the time of the fusing drive is greater than aproportion of a maximum current value with respect to an average currentvalue in the anode period of the at least one electrode in the rateddrive of the steady operation mode.
 15. The light source apparatusaccording to claim 14, further comprising: an evaluating portion thatdetermines a condition of the arc tube, the drive unit, at the time ofthe fusing drive of the initial operation mode, increasing theproportion of the maximum current value of the current waveform withrespect to the average current value in the anode period of the at leastone of the first electrode and the second electrode, at the time of thefusing drive, in accordance with a degree of erosion determined by theevaluating portion.
 16. The light source apparatus according to claim 1,the drive unit, as an aspect of the fusing drive of the initialoperation mode, is capable of carrying out, for one fusing drive, eitherone of a first fusing drive, which melts the leading extremity side ofthe first electrode more than the leading extremity side of the secondelectrode, or a second fusing drive, which melts the leading extremityside of the second electrode more than the leading extremity side of thefirst electrode, and the drive unit, by carrying out the second fusingdrive as a fusing drive of a current initial operation in the event thatthe first fusing drive has been carried out as a fusing drive of animmediately preceding initial operation, and carrying out the firstfusing drive as the fusing drive of the current initial operation in theevent that the second fusing drive has been carried out as the fusingdrive of the immediately preceding initial operation, alternately makesthe first electrode and the second electrode a main fusion subject. 17.A drive method of a light source apparatus carrying out a steadyoperation supplying a steady energy to a first electrode and a secondelectrode of a discharge light emitting type arc tube and, beforecarrying out the steady operation, carrying out an initial operationsupplying energy to the first electrode and the second electrode, withan operation differing from the steady operation, the method comprising:carrying out a fusing drive making a volume of a fused portion of aleading extremity side of at least one of the first electrode and thesecond electrode, in the initial operation greater than a volume of thefused portion of the leading extremity side of the at least one of thefirst electrode and the second electrode at a time of a rated driveduring the steady operation.
 18. A projector comprising: the lightsource apparatus according to claim 1; a light modulating deviceilluminated by an illumination light from the light source apparatus;and a projection optical system that projects an image formed by thelight modulating device.